A Computational Investigation of the Nitrogen-Boron Interaction in
o-(N,N-Dialkylaminomethyl)arylboronate Systems
Joseph D. Larkin,*,† John S. Fossey,‡ Tony D. James,§ Bernard R. Brooks,† and
Charles W. Bock|
National Heart, Lung, and Blood Institute, The National Institutes of Health, Building 50,
Bethesda, Maryland 20851, United States, School of Chemistry, UniVersity of Birmingham, Edgbaston,
Birmingham B15 2TT, U.K., Department of Chemistry, UniVersity of Bath, Bath BA2 7AY, U.K., Department of
Chemistry and Biochemistry, School of Science and Health, Philadelphia UniVersity, School House Lane and
Henry AVenue, Philadelphia, PennsylVania 19144, United States, and The Institute for Cancer Research, Fox
Chase Cancer Center, 7701 Burholme AVenue, Philadelphia, PennsylVania 19111, United States
ReceiVed: September 14, 2010; ReVised Manuscript ReceiVed: October 8, 2010
o-(N,N-Dialkylaminomethyl)arylboronate systems are an important class of compounds in diol-sensor
development. We report results from a computational investigation of fourteen o-(N,N-dialkylaminomethyl)-
arylboronates using second-order Møller-Plesset (MP2) perturbation theory. Geometry optimizations were
performed at the MP2/cc-pVDZ level and followed by single-point calculations at the MP2/aug-cc-pVDZ(cc-
pVTZ) levels. These results are compared to those from density functional theory (DFT) at the
PBE1PBE(PBE1PBE-D)/6-311++G(d,p)(aug-cc-pVDZ) levels, as well as to experiment. Results from
continuum PCM and CPCM solvation models were employed to assess the effects of a bulk aqueous
environment. Although the behavior of o-(N,N-dialkylaminomethyl) free acid and ester proved to be
complicated, we were able to extract some important trends from our calculations: (1) for the free acids the
intramolecular hydrogen-bonded B-O-H · · ·N seven-membered ring conformers 12 and 16 are found to be
slightly lower in energy than the dative-bonded NfB five-membered ring conformers 10 and 14 while
conformers 13 and 17, with no direct boron-nitrogen interaction, are significantly higher in energy than 12
and 16; (2) for the esters where no intramolecular B-O-H · · ·N bonded form is possible, the NfB conformers
18 and 21 are significantly lower in energy than the no-interaction forms 20 and 23; (3) H2O insertion reactions
into the NfB structures 10, 14, 18, and 21 leading to the seven-membered intermolecular hydrogen-bonded
B · · ·OH2 · · ·N ring structures 11, 15, 19, and 22 are all energetically favorable.
Introduction
The so-called coordinative or dative nitrogen-to-boron NfB
bonds have been studied for many years.1 The strength of these
NfB bonds depends greatly on the substituents at both atoms;
electron withdrawing groups increase the Lewis acidity of boron,
while electron donating groups increase the Lewis basicity at
nitrogen. In considering NfB bond strengths it is necessary to
balance these electronic factors against the counteracting steric
requirements of the same substituents. An investigation of 144
compounds with NfB bonds concluded that steric interactions,
as well as ring strain (in the case of cyclic diesters) weaken
and elongate the NfB bond, which occurs with a concurrent
reduction in the tetrahedral geometry of the boron center.2
The N-methyl-o-(phenylboronic acid)-N-benzylamine (1)
system has been investigated separately by a number of
groups.3–5 Scheme 1 depicts a general model where, at one
extreme, the acyclic forms (1 and 2) illustrate a separate nitrogen
and boron center and, at the other, the cyclic forms (4 and 5)
illustrate a full NfB bond; the species existing in equilibrium
in an aqueous environment. Species 3 involves a protonated
nitrogen, and this ammonium cation precludes any nitrogen-
boron interaction.
The energy of various nitrogen-boron interactions has been
calculated from the stepwise formation constants of potentio-
metric titrations. On the basis of the relative stabilities of ternary
phosphate complexes, James and co-workers estimated that
nitrogen-boron interactions are approximately between +3.6
and +6.0 kcal/mol in N-methyl-o-(phenylboronic acid)-N-
benzylamine.3
The Wang group,6 using GGA DFT methodology7 and the
COSMO implicit solvent model8,9 estimated the strength of the
NfB bond for [o-(trimethylamino)phenyl]boronic acids to be
+3.1 kcal/mol or less. On the basis of these results, it appears
that the strength of a nitrogen-boron interaction in solution is
similar to that of a hydrogen bond in bulk water.10,11 While this
makes the interaction a weak one it does explain the importance
of the NfB bond in saccharide sensors. It is the weakness of
the NfB bond that explains why it is a central feature in many
fluorescent PET sensors playing a pivotal role in signaling the
binding event.12,13 If this interaction were much stronger, then
the binding of a diol would not be able to disrupt the
nitrogen-boron interaction sufficiently so as to modulate a
change in fluorescence. By the same token, if the interaction
were much weaker then there would be no significant intramo-
lecular nitrogen-boron interaction to disrupt in the first place.
For some time the formation of a NfB dative bond between
nitrogen and boron was assumed to be responsible for the
fluorescence enhancement seen when boronic acids bound
diols.12–24 This interpretation does, however, raise certain
† The National Institutes of Health.
‡ University of Birmingham.
§ University of Bath.
| Philadelphia University and Fox Chase Cancer Center.
J. Phys. Chem. A 2010, 114, 12531–12539 12531
10.1021/jp1087674  2010 American Chemical Society
Published on Web 11/05/2010

questions. The fluorescence recovery in these systems functions
as a digital “off-on” response. Fluorescence emission returns
to the same maximal value regardless of the observed stability
constant (Kobs) of the ligand or the pKa′ of the resulting boronate
ester. It is known that the acidity of boron influences the strength
of the NfB bond.25 Therefore, if a NfB bond did modulate
PET, we might necessarily expect the fluorescence response to
vary as a function of the degree of acidity or strength of
complexation, but this is not the case;26 moreover, numerical
values of +3.6 to +6.0 kcal/mol do not agree with the
interpretation of a NfB bond.3
The single-crystal X-ray structure of sensor 6 (see Figure 1),
in both its bound and unbound state, has recently been
published.27 In the case of the unbound receptor the geometry
at boron is nearly trigonal planar. This is important, as the
absence of minimal deviation from planarity implies that there
is little or no direct NfB Lewis base-Lewis acid bond at boron.
When bound to tartaric acid, the complex was crystallized from
a methanol and dichloromethane solution. In the resulting tartrate
complex, two molecules of methanol, one at each boron center,
are bound through their oxygen atoms to their respective boron
centers. While the hydrogen atoms of methanol could not be
directly located in these single-crystal X-ray structures, it is not
unreasonable to infer from the geometry that each oxygen atom
is dative-bonded to the boron center and hydrogen-bonded to
the adjacent nitrogen atom. Oxygen to boron and oxygen to
nitrogen bond distances of around 3.5 and 2.7 Å, respectively,
were reported in this case (Figure 1).
While speculative, this structural interpretation of the interac-
tion between boronic acid and the proximal tertiary amine
through a bound protic solvent molecule (solvent insertion into
the NfB bond) corresponds well with contemporary computa-
tional and potentiometric titration data, in which the formation of
intramolecular seven-membered rings should not be ignored.3,28–30
In particular, the X-ray crystal structure above and bond
strengths determined from potentiometric titrations of between
+3.6 and +6.0 kcal/mol are comparable to a hydrogen bonding
interaction manifested through a bound solvent molecule at the
boron center.3,28–30
An infrared study into the interaction between nitrogen and
boron in a related system indicated that hydrogen bonding to a
nitrogen through a bound solvent molecule at the boron center
was possible.31 The experimental rationale was based on
comparing two emergent peaks in infrared spectra to similar
peaks in known model systems. The results indicated that in
carbon tetrachloride the interaction between the nitrogen and
boron of 8-quinolineboronic acid could be modulated by
either water or phenol bound to the boron center at oxygen,
see Figure 2.
Anslyn and co-workers recently performed structural inves-
tigations into the nitrogen-boron interaction in o-(N,N-dialkyl-
aminomethyl)arylboronate systems (i.e., o-(pyrrolidinylmethyl)-
phenylboronate).32,33 From detailed 11B-NMR measurements and
X-ray data it was shown that in an aprotic solvent, the NfB
bond is usually present. However, in a protic media, solvent
insertion into the NfB bond occurs to afford a hydrogen-
bonded zwitterionic species. These authors further supported
SCHEME 1: Extent of the Interaction between Nitrogen and Boron Illustrated within the Upper and Lower Bounds of
Possible Contact Depicted as the Cyclic and Acyclic Forms3
Figure 1. Single-crystal X-ray structure of the S,S-diboronic acid (S,S-
6)-L-tartaric acid complex isolated by James and co-workers.27 While
the hydrogen atoms of methanol were not directly located, it can be
inferred that the geometries between the bound and unbound receptors
will be similar; each oxygen atom will therefore concurrently bind to
the boron center and hydrogen bond to the nitrogen atom. Boron to
nitrogen bond distances of around 3.5 Å were reported [B(1) · · ·N(1)
) 3.430 Å and B(2) · · ·N(2) ) 3.500 Å]. Oxygen to nitrogen bond
distances of around 2.7 Å were reported [N(1) · · ·O(1) ) 2.655 Å and
N(2) · · ·O(2) ) 2.693 Å]. Atoms marked in red represent oxygen, pink
boron, gray carbon, and blue nitrogen. For clarity hydrogen atoms are
not displayed. The red dotted lines represent hydrogen bonds.
12532 J. Phys. Chem. A, Vol. 114, No. 47, 2010 Larkin et al.

their findings by calculations at the B3LYP/6-31+G(d,p)//
B3LYP/6-31+G(d,p) computational level in a simulated water
continuum. Unfortunately, it is well-known that the B3LYP
functional with a variety of basis sets has significant problems
predicting the presence and strength of NfB bonds; thus, some
caution needs to be exercised in interpreting these B3LYP
computational results.29,34–39 Thanks to the experimental and
computational investigations by Anslyn32,33 and a number of
other groups3,6,26 it appears from both experimental and com-
putational studies that a variety of structural variations of the
nitrogen-boron interaction, i.e., NfB (4), B-O-H · · ·N (9a),
and B · · ·OHR · · ·N (9b) (see Scheme 1 and Figure 3) need to
be carefully considered for individual boronic acid systems.
In this article we report results from a computational
investigation of fourteen o-(N,N-dialkylaminomethyl)arylbor-
onate systems organized into four groups (Figure 4). Each group
contains a molecule with a NfB bond cf compound 10, a
solvent inserted system (B · · ·OH2 · · ·N), compound 11, and an
extreme case where the nitrogen and boron centers are separated
to a point where no NfB bond is possible, compound 13.
Groups 1 and 2 also contain molecules with intramolecular
B-O-H · · ·N cyclic hydrogen bonds, 12. The first group
consists of the boronic acids 10-13; the second group consists
of the mono methyl ester of boronic acid 14-17; the third group
consists of the dimethyl boronic esters 18-20; and the fourth
group consists of the cyclic boronic esters 21-23.
These four groups were chosen for this investigation because
they represent a stepwise transition between the free boronic
acid (group 1) and the fully esterified boronic acids (groups 3
and 4). Including both groups 3 and 4 in this investigation
enabled us to compare the difference between acyclic ester and
cyclic ester formation. Using these simple model systems, we
employed computational methods to understand the relative
energies of NfB dative-bonded and B-O-H · · ·N hydrogen-
bonded conformers, as well as the thermochemistry of solvent
insertion into NfB forms that yield structures involving a
B · · ·OHR · · ·N linkage. Results from our systematic investiga-
tion will provide support for distinguishing which of the three
boron-nitrogen coordinated structures is present in o-(N,N-
dialkylaminomethyl)arylboronate systems at neutral pH or in
protic media.
Computational Methods
Equilibrium geometries for the structures described in this
article were obtained using second-order Møller-Plesset (MP2)
perturbation theory40 with the frozen core (FC) option, which
neglects core-electron correlation; the Dunning-Woon cor-
relation-consistent (cc) cc-pVDZ basis set was employed for
the initial optimizations;41–44 single-point calculations at this
MP2/cc-pVDZ geometry were also carried out at the MP2(FC)/
aug-cc-pVDZ and MP2/cc-pVTZ computational levels. For
comparison, we also performed optimizations at the MP2/6-
31+G(d) level.45 Frequency analyses were performed analyti-
cally at the MP2/cc-pVDZ//MP2/cc-pVDZ level to confirm that
the optimized structures were local minima on the PES and to
correct reaction enthalpies and free energies to 298 K. All
calculations were carried out using either the GAUSSIAN 0346
or GAUSSIAN 0947 suite of programs. Bonding was analyzed
with the aid of natural bond orbitals (NBOs).48–51
Geometry optimizations using MP2 methodology with aug-
mented correlation-consistent (cc) basis sets are not currently
practical for detailed investigations of the larger boron deriva-
tives of primary chemical interest. Density functional theory
(DFT) with Pople-style split-valence basis sets52,53 provides an
economical alternative, but the reliability of specific functional/
basis set combinations for describing the incredibly diverse
range54 of boron chemistry has yet to be fully established. Thus,
our MP2 results were compared to those using the hybrid
PBE1PBE functional,55,56 which makes use of the one-parameter
generalized-gradient approximation (GGA) PBE functional with
a 25% exchange and 75% correlation weighting.57 Our experi-
ence with a variety of PBE1PBE computational levels is that
this functional does reasonably well in describing NfB bonds
when compared to the corresponding MP2 results;29,34,35,39 in
contrast, the B3LYP functional does not describe such bonds
reliably.29,34–39 Additional PBE1PBE calculations that empirically
incorporate the effects of dispersion58 were performed using
QChem 3.2.59
Results from continuum solvation models were employed to
assess the effects of a bulk aqueous environment on the gas-
phase results.60 We employed the following implicit solvation
models: (1) the IEF polarizable continuum model (PCM) model,
developed by Tomasi and co-workers61–65 and (2) the conductor-
like PCM model (CPCM), introduced by Barone and Cossi.66,67
(The UAKS cavity was used for the CPCM solvent model based
on the performance indicated by Takano and Houk.68) As is
well-known, such continuum models only provide a description
of long-range interactions and have specific limitations in
describing protic solvents.69,70 Obviously, for the solvent inserted
models we investigated, it was necessary to include an explicit
water molecule in the calculations.
Results and Discussion
MP2. Calculations were performed on the model o-(N,N-
dialkylaminomethyl)arylboronates 10-23 to investigate the
factors influencing the balance between the NfB bonded
conformers (10, 14, 18, and 21), the B · · ·OH2 · · ·N solvent
inserted forms (11, 15, 19, and 22), the B-O-H · · ·N intramo-
lecular hydrogen-bonded conformers (12 and 16), and those with
separated nitrogen and boron centers (13, 17, 20, and 23), see
Figure 4.
As would be expected, the structures with the nonbonded
boron and nitrogen centers in all four groups (13, 17, 20, and
23), were calculated to be consistently higher in energy than
the corresponding NfB bonded conformers (10, 14, 18, and
21); furthermore, structures 13 and 17 in groups 1 and 2 were
Figure 2. Morrison’s proposed complexes of the cis-1,2-cyclopen-
tanediol ester of 8-quinolineboronic acid with solvent water and phenol
molecules bridging the nitrogen and boron centers.31
Figure 3. B-O-H · · ·N (9a) intramolecular hydrogen-bonded and
B · · ·OHR · · ·N (9b) solvent-inserted structures.
N-B Interaction in o-(N,N-Dialkylaminomethyl)arylboronate J. Phys. Chem. A, Vol. 114, No. 47, 2010 12533

calculated to be higher in energy than the B-O-H · · ·N
intramolecular hydrogen-bonded conformers (12 and 16). The
thermochemistry of the conversions 10 f 13, 14 f 17, 18 f
20, and 21 f 23 at various MP2 levels are listed in Table 1A
and provide some measure of the strength of the NfB dative
bond in these o-(N,N-dialkylaminomethyl)arylboronate systems;
diffuse functions clearly increase the endothermicity of these
processes by some 2 kcal/mol, compare columns 2 and 3. The
values of ∆E for these conversions range from +8.3 to +11.9
kcal/mol at the MP2/aug-cc-pVDZ//MP2/cc-pVDZ level and
from +6.8 to +9.7 kcal/mol at the MP2/cc-pVTZ//MP2/cc-
pVDZ level; thermal corrections calculated at the MP2/6-
31+G(d)//MP2/6-31+G(d) and MP2/cc-pVDZ//MP2/cc-pVDZ
levels indicate the values of ∆E are within a few tenths of a
kcal/mol of the corresponding values of ∆H2980 . Interestingly,
these computational estimates are significantly higher than
previous estimates of the strength of the NfB dative bond in
such systems, which range from +3.6 to +6.0 kcal/mol,3,28–30
on the basis of the relative stabilities of ternary phosphate
complexes in N-methyl-o-(phenylboronic acid)-N-benzylamine.3
There is also general agreement from the MP2 computational
results in Table 1A that the B-O-H · · ·N intramolecular
hydrogen-bonded conformers of the free acids 12 and 16 are
slightly lower in energy in vacuo than the corresponding dative-
bonded NfB conformers 10 and 14; e.g., the values of ∆E for
the 10f 12 and 14f 16 conversions are -0.7 and -0.9 kcal/
mol, respectively, at the MP2/aug-cc-pVDZ//MP2/cc-pVDZ
level. This small energy difference suggests that intramolecular
NfB dative bonds and B-O-H · · ·N hydrogen bonds are
similar in strength in these o-(N,N-dialkylaminomethyl)arylbo-
ronate systems. The slightly higher energy of the dative-bonded
forms might be the result of some strain in the five-membered
NfB bonded ring structure.
Additionally, reactions involving an explicit water molecule
inserted into the NfB dative bond, which result in the structures
11, 15, 19, and 22 shown schematically in Figure 4, are
calculated to be thermodynamically favored in vacuo at all the
MP2 levels we considered (Table 1A); to the authors knowledge
this is the first time this has been reported in the gas phase. It
is clear from this table that basis set effects can significantly
alter the calculated reaction thermochemistry; e.g., the values
of ∆E for these insertions at the MP2/cc-pVDZ//MP2/cc-pVDZ
level are some 3-4 kcal/mol more negative in energy than the
MP2/aug-cc-pVDZ//MP2/cc-pVDZ values; the corresponding
values at the MP2/cc-pVTZ//MP2/cc-pVDZ are in much better
agreement with the MP2/aug-cc-pVDZ//MP2/cc-pVDZ values.
DFT. The number of atoms involved in the o-(N,N-dialkyl-
aminomethyl)arylboronate model systems we investigated with
MP2 methodology severely limited the correlation-consistent
basis sets we could employ for the geometry optimization of
these structures; specifically, our computer resources restricted
us to the Dunning-Woon cc-pVDZ basis set for optimizations
that do not include diffuse functions. In view of the role that
diffuse functions play in the MP2 thermochemistry of 10-23
noted above (Table 1A), we decided to reoptimize these
structures by employing the more economical DFT methodology
using the PBE1PBE functional with the larger 6-311++G(d,p)
and aug-cc-pVDZ basis sets that explicitly include diffuse
functions.29,34,35,39 Interestingly, overlaying the MP2/cc-pVDZ,
PBE1PBE/6-311++G(d,p), and PBE1PBE/aug-cc-pVDZ op-
timized structures showed no significant variation in the
geometry as a result of altering the computational methodology
from MP2 to PBE1PBE and increasing the size of the basis set
(Figure 1S in the Supporting Information). Furthermore, the
trends observed for the PBE1PBE reaction energetics are
generally in accord with those seen at the various MP2 levels
we employed (compare Table 1A,B); although some details are
different. For example, the predicted values of ∆E at the various
PBE1PBE levels for the conformer conversions 10 f 13, 14
f 17, 18 f 20, and 21 f 23 suggest that the strength of the
NfB dative bond in structures 10, 14, 18, and 21 is substantially
less than the corresponding MP2 estimates, in much closer
agreement with the experimental range of +3.6 to +6.0
kcal/mol.3,28–30 Some caution is required here because these GGA
Figure 4. o-(N,N-dialkylaminomethyl)arylboronates 10-23 optimized in this investigation.
12534 J. Phys. Chem. A, Vol. 114, No. 47, 2010 Larkin et al.

calculations do not adequately treat dispersion (see below). Of
course, the diminution of the predicted PBE1PBE NfB bond
strength is reflected in higher exothermicities at this level for
the NfB to B-O-H · · ·N conversions. The values of ∆E for
the hydrogen insertion reactions are all negative at the various
PBE1PBE levels and are in reasonable accord with the results
from the comparable MP2 calculations.
Considering the well-known failure of the more popular
hybrid and GGA functionals to properly describe weak van der
Waals interactions,71,72 in conjunction with the relatively small
energy differences between some conformers of the o-(N,N-
dialkylaminomethyl)arylboronate model systems involved in this
investigation, we felt it necessary to perform single-point energy
calculations of the PBE1PBE optimized geometries with the
PBE1PBE-D functional using the same basis sets (Table 1C).
The PBE1PBE-D functional incorporates the empirical disper-
sion correction of Grimme;58 the QChem 3.2 package was
employed for these calculations because it is the only code we
have access to that has PBE1PBE-D implemented.47 To avoid
possible double-counting of dispersion effects, the energetics
of reactions that included an explicit water molecule, e.g., 10
+ H2Of 11, have not been included in the table. An excellent
discussion of this problem has been provided by Barone et al.;73
our results for these hydration reactions with the PBE1PBE-D
functional support their conclusions.
The addition of these empirical dispersion corrections for
conformer conversions such as 10 f 12(13) does not qualita-
tively change the order of the relative energies of the o-(N,N-
dialkylaminomethyl)arylboronates conformers noted in Table
1A (MP2) or Table 1B (PBE1PBE). However, as one might
anticipate, it drives the PBE1PBE conformer conversion energies
closer to those found with the MP2 calculations. The results of
these PBE1PBE-D calculations further emphasize the necessity
of taking into account NfB dative bonded and B-O-H · · ·N
intramolecular hydrogen-bonded conformers when trying to
improve the diol-sensor capabilities of o-(N,N-dialkylamino-
methyl)arylboronate systems.
In PCM and CPCM Aqueous Solvent. To assess the long-
range effects an aqueous solvent may play in determining the
structures and energetics of the o-(N,N-dialkylaminomethyl)-
arylboronate systems 10-23, all fourteen of the gas-phase
structures were reoptimized in the PCM and CPCM reaction
TABLE 1: Reaction Energies, ∆E (∆H2980 ) (kcal/mol), in Vacuo at the (A) MP2/6-31+G(d)//MP2/6-31+G(d), MP2/
6-311++G(d,p)//MP2/6-311++G(d,p), MP2/cc-pVDZ//MP2/cc-pVDZ, MP2/aug-cc-pVDZ//MP2/cc-pVDZ, and MP2/cc-pVTZ//
MP2/cc-pVDZ; (B) PBE1PBE/6-31+G(d)//PBE1PBE/6-31+G(d), PBE1PBE/6-311++G(d,p)//PBE1PBE/6-311++G(d,p),
PBE1PBE/cc-pVDZ//PBE1PBE/cc-pVDZ, and PBE1PBE/aug-cc-pVDZ//PBE1PBE/aug-cc-pVDZ; and (C) PBE1PBE-D/
6-31+G(d)//PBE1PBE/6-31+G(d), PBE1PBE-D/6-311++G(d,p)//PBE1PBE/6-311++G(d,p), PBE1PBE-D/cc-pVDZ//PBE1PBE/
cc-pVDZ, and PBE1PBE-D/aug-cc-pVDZ//PBE1PBE/aug-cc-pVDZ Computational Levels
A. MP2
reaction/level
MP2/6-31+G(d)//
MP2/6-31+G(d)
MP2/6-311++G(d,p)//
MP2/6-31+G(d)
MP2/cc-pVDZ//
MP2/cc-pVDZ
MP2/aug-cc-pVDZ//
MP2/cc-pVDZ
MP2/cc-pVTZ//MP2/
cc-pVDZ
∆E(∆H2980 ) (kcal/mol)
10 + H2O f 11 -3.1 (-1.2) -2.6 -6.9 (-5.6) -2.4 -3.2
10 f 12 -1.0 (-0.4) -1.2 -3.3 (-2.7) -0.7 -1.9
10 f 13 +9.5 (+9.7) +8.8 +7.5 (+7.7) +9.6 +8.0
14 + H2O f 15 -6.3 (-3.7) -3.2 -7.9 (-6.7) -3.5 -3.6
14 f 16 -1.9 (-1.3) -1.9 -3.8 (-3.2) -0.9 -1.2
14 f 17 +8.2 (+8.5) +7.8 +6.8 (+7.1) +9.0 +8.5
18 + H2O f 19 -9.2 (-6.8) -6.4 -11.3 (-10.0) -6.8 -8.0
18 f 20 +7.7 (+7.7) +7.0 +6.8 (+6.8) +8.3 +6.8
21 + H2O f 22 -6.0 (-3.6) -2.8 -7.3 (-5.9) -2.7 -4.4
21 f 23 +10.8 (+11.0) +10.0 +9.2 (+9.3) +11.9 +9.7
B. PBE1PBE
reaction/level
PBE1PBE/6-31+G(d)//
PBE1PBE/6-31+G(d)
PBE1PBE/6-311++G(d,p)//
PBE1PBE/6-311++G(d,p)
PBE1PBE/cc-pVDZ//PBE1PBE/
cc-pVDZ
PBE1PBE/aug-cc-pVDZ//
PBE1PBE/aug-cc-pVDZ
10 + H2O f 11 -5.8 (-3.8) -3.3 (-1.7) -9.4 (-8.2) -2.6 (-1.0)
10 f 12 -5.1 (-4.6) -4.8 (-4.3) -5.2 (-5.8) -4.3 (-3.8)
10 f 13 +5.2 (+5.3) +4.8 (+5.0) +4.7 (+4.8) +5.0 (+5.1)
14 + H2O f 15 -6.5 (-4.5) -4.1 (-2.5) -10.7 (-9.8) -3.2 (-1.7)
14 f 16 -6.3 (-5.8) -6.0 (-5.5) -6.4 (-5.9) -5.2 (-4.9)
14 f 17 +3.9 (+4.0) +3.5 (+3.7) +3.6 (+3.8) +3.9 (+3.9)
18 + H2O f 19 -9.7 (-7.8) -7.2 (-5.7) -13.9 (-12.9) -6.2 (-4.8)
18 f 20 +2.3 (+2.3) +2.0 (+2.0) +2.7 (+2.7) +2.5 (+2.5)
21 + H2O f 22 -6.5 (-4.7) -4.1 (-2.7) -10.5 (-9.5) -3.1 (-1.7)
21 f 23 +4.4 (+4.5) +4.1 (+4.2) +4.0 (+4.0) +4.8 (+4.8)
C. PBE1PBE-Da
reaction/level
PBE1PBE-D/6-31+G(d)//
PBE1PBE/6-31+G(d)
PBE1PBE-D/6-311++G(d,p)//
PBE1PBE/6-311++G(d,p)
PBE1PBE-D/cc-pVDZ//
PBE1PBE/cc-pVDZ
PBE1PBE-D/aug-cc-pVDZ//
PBE1PBE/aug-cc-pVDZ
10f 12 -3.8 -3.6 -4.0 -2.9
10f 13 +8.0 +7.5 +7.5 +7.9
14f 16 -4.0 -3.8 -4.2 -3.0
14f 17 +7.5 +7.2 +7.3 +7.6
18f 20 +6.9 +6.6 +7.0 +7.3
21f 23 +8.7 +8.6 +8.4 +9.2
a These calculations were all performed with QChem 3.2 using a grid with 75 radial shells and 302 angular points.
N-B Interaction in o-(N,N-Dialkylaminomethyl)arylboronate J. Phys. Chem. A, Vol. 114, No. 47, 2010 12535

fields of water at the MP2/cc-pVDZ//MP2/cc-pVDZ level; these
optimizations were followed by single-point calculations at the
MP2/aug-cc-pVDZ//MP2/cc-pVDZ and MP2/cc-pVTZ//MP2/
cc-pVDZ levels (Table 2A,B). Additional optimizations in these
aqueous environments using DFT methodology at the PBE1PBE/
6-311++G(d,p) and PBE1PBE/aug-cc-pVDZ levels were also
performed (Table 2C,D).
In general, the thermochemical trends noted above for
calculations in vacuo are also observed in PCM and CPCM
aqueous solution (compare corresponding results in Tables 1
TABLE 2: Reaction Energies, ∆E (∆H2980 ) (kcal/mol), in PCM and CPCM Implicit Aqueous Media at the (A) PCM(MP2)
MP2/cc-pVDZ//MP2/cc-pVDZ, MP2/cc-pVDZ//MP2/cc-pVDZ, and MP2/cc-pVTZ//MP2/cc-pVDZ; (B) CPCM(MP2) MP2/
cc-pVDZ//MP2/cc-pVDZ, MP2/cc-pVDZ//MP2/cc-pVDZ, and MP2/cc-pVTZ//MP2/cc-pVDZ; (C) PCM(PBE1PBE) PBE1PBE/
6-31+G(d), PBE1PBE/6-311++G(d,p), PBE1PBE/cc-pVDZ, and PBE1PBE/aug-cc-pVDZ; and (D) CPCM(PBE1PBE)
PBE1PBE/6-31+G(d), PBE1PBE/6-311++G(d,p), PBE1PBE/cc-pVDZ, and PBE1PBE/aug-cc-pVDZ Computational Levels
A. PCM(MP2)
reaction/level
PCM: MP2/cc-pVDZ//
MP2/cc-pVDZ
PCM: MP2/aug-cc-pVDZ//
MP2/cc-pVDZ
PCM: MP2/cc-pVTZ//MP2/
cc-pVDZ
10 + H2O f 11 -5.5 (-3.3) -3.5 -3.4
10 f 12 +0.2 (+0.2) +3.3 +2.0
10 f 13 +11.1 (+10.9) +13.8 +12.1
14 + H2O f 15 -7.5 (-5.3) -3.5 -4.8
14 f 16 -0.7 (-0.6) +2.7 +0.9
14 f 17 +10.3 (+12.6) +12.9 +11.4
18 + H2O f 19 -11.2 (-8.8) -7.2 -8.5
18 f 20 +9.4 (+9.3) +10.8 +9.3
21 + H2O f 22 -7.4 (-5.1) -3.0 -4.8
21 f 23 +12.5 (+12.3) +15.5 +13.3
B. CPCM(MP2)
reaction/level
CPCM: MP2/cc-pVDZ//
MP2/cc-pVDZ
CPCM: MP2/aug-cc-pVDZ//
MP2/cc-pVDZ
CPCM: MP2/cc-pVTZ//
MP2/cc-pVDZ
10 + H2O f 11 -4.3 (-1.7) -1.5 -2.2
10 f 12 -1.0 (-1.2) +2.1 +0.8
10 f 13 +7.9 (+7.4) +11.6 +10.0
14 + H2O f 15 -7.7 (-5.7) -2.9 -4.3
14 f 16 -1.4 (-1.7) +2.3 +0.6
14 f 17 +8.9 (+8.4) +11.6 +9.9
18 + H2O f 19 -10.9 (-8.7) -6.4 -7.9
18 f 20 +8.7 (+8.3) +10.2 +8.7
21 + H2O f 22 -7.2 (-5.1) -2.4 -4.4
21 f 23 +11.5 (+11.1) +14.4 +12.3
C. PCM(PBE1PBE)
reaction/level
PCM:
PBE1PBE/6-31+G(d)//
PBE1PBE/6-31+G(d)
PCM:
PBE1PBE/6-311++G(d,p)//
PBE1PBE/6-311++G(d,p)
PCM:
PBE1PBE/cc-pVDZ//
PBE1PBE/cc-pVDZ
PCM:
PBE1PBE/aug-cc-pVDZ//
PBE1PBE/aug-cc-pVDZ
10 + H2O f 11 -5.4 (-2.8) -3.0 (-0.6) -8.4 (-6.2) -3.1 (-0.7)
10f 12 -1.5 (-1.6) -1.3 (-1.5) -2.3 (-2.3) -0.8 (-1.1)
10f 13 +9.0 (+8.8) +8.6 (+8.4) +8.1 (+7.9) +8.9 (+8.6)
14 + H2Of 15 -6.0 (-3.4) -3.8 (-1.5) -10.8 (-8.7) -3.8 (-1.5)
14f 16 -3.1 (-3.1) -2.9 (-3.0) -3.8 (-3.8) -2.3 (-2.4)
14f 17 +6.9 (+6.7) +6.9 (+6.7) a +7.2 (+7.0)
18 + H2Of 19 -9.5 (-6.7) -7.0 (-4.5) -15.2 (-14.0) -7.0 (-4.6)
18f 20 +4.8 (+4.6) +4.6 (+4.4) a +5.1 (+4.9)
21 + H2Of 22 -6.5 (-4.0) -4.2 (-1.9) -10.9 (-8.9) -4.1 (-1.9)
21f 23 +8.2 (+8.0) +7.9 (+7.8) +7.4 (+7.3) +8.3 (+8.1)
D. CPCM(PBE1PBE)
reaction/level
CPCM:
PBE1PBE/6-31+G(d)//
PBE1PBE/6-31+G(d)
CPCM:
PBE1PBE/6-311++G(d,p)//
PBE1PBE/6-311++G(d,p)
CPCM:
PBE1PBE/cc-pVDZ//
PBE1PBE/cc-pVDZ
CPCM:
PBE1PBE/aug-cc-pVDZ//
PBE1PBE/aug-cc-pVDZ
10 + H2Of 11 -4.4 (-1.7) -1.9 (+0.5) -6.6 (-4.6) -2.0 (+0.4)
10f 12 -2.4 (-2.7) -2.4 (-2.7) -3.3 (-3.5) -1.9 (-2.4)
10f 13 +6.8 (+6.2) +5.7 (+5.1) +6.0 (+5.5) +8.2 (+7.2)
14 + H2Of 15 -5.3 (-2.8) -3.9 (-1.6) +5.7 (+8.0) -3.0 (-0.7)
14f 16 -3.1 (-3.3) -4.0 (-4.3) -4.0 (-4.3) -2.5 (-2.8)
14f 17 +5.2 (+4.7) +4.9 (+4.4) +5.8 (+5.4) +7.9 (+6.9)
18 + H2Of 19 -8.9 (-6.3) -6.4 (-4.0) -7.9 (-6.5) -6.2 (-3.8)
18f 20 +4.0 (+3.7) +3.8 (+3.4) -3.8 (-5.1) +4.6 (+4.2)
21 + H2Of 22 -6.1 (-3.7) -3.7 (-1.5) -4.5 (-3.1) -3.5 (-1.4)
21f 23 +7.1 (+6.7) +6.8 (+6.3) -4.0 (-5.0) +8.5 (+7.2)
a All attempts at computing geometric minima for structures 17 and 20 were unsuccessful.
12536 J. Phys. Chem. A, Vol. 114, No. 47, 2010 Larkin et al.

and 2), although there is an increase in the conformer conversion
and explicit hydration reaction energies when the effects of these
implicit solvation models are included. Interestingly, the 10 f
12 and 14 f 16 conformer conversions at the MP2/aug-cc-
pVDZ//MP2/cc-pVDZ and MP2/cc-pVTZ//MP2/cc-pVDZ levels
suggest that the NfB bonded conformers are slightly lower in
energy than the B-O-H · · ·N conformers in aqueous solution,
contrary to what we found in the gas phase. These calculations
show that the description of the intramolecular interaction
between nitrogen and boron in o-(N,N-dialkylaminomethyl)aryl-
boronate systems in aqueous media is quite complex and may
involve a combination of NfB, B-O-H · · ·N, and B · · ·
OH2 · · ·N structures; additional experimental and computational
studies need to be performed to establish how to tune this
interaction to enhance the role of one or the other of these
structural moieties and to better exploit the pertinent chemical
properties of each for various applications.
In contrast to the computational findings from the Anslyn
group32 at the B3LYP/6-31+G(d,p)//B3LYP/6-31+G(d,p) level,
our findings on o-(N,N-dialkylaminomethyl)arylboronic acid 10
in Figure 4 at several MP2 and PBE1PBE levels indicate that
the NfB bonded structures are indeed local minima on the PESs
for the model o-(N,N-dialkylaminomethyl)arylboronic acids we
considered in this paper (the shortest N · · ·B distance in the
o-(N,N-dialkylaminomethyl)arylboronic acid (i.e., o-(pyrrolidi-
nylmethyl)phenylboronic acid) structures reported by Anslyn32
was ∼2.7 Å, whereas results at the MP2 and PBE1PBE methods
of this study predict much shorter distances, 1.768-1.860 Å
(Table 1S and 2S, Supporting Information)) indicative of a
boron-nitrogen dative bond; this difficulty with describing
intramolecular NfB bonding in boronic acids appears to be
symptomatic of B3LYP methodology.29,34–39 On the other hand,
there are some areas of agreement with our calculations and
those of Anslyn and co-workers;32 e.g., the boronate ester
(formed from the reaction of an o-(N,N-dialkylaminomethyl)-
arylboronic acid (i.e., o-(pyrrolidinylmethyl)phenylboronic acid)
with catechol) had a clear NfB dative bond with a N-B
distance of 1.80 Å; consistent with our structure 21, which has
a calculated range of N-B distances of 1.731-1.790 Å (Tables
1S and 2S, Supporting Information). Other energy minimized
structures elucidated by Anslyn and co-workers32,33 are com-
parable to our structures 10, 11, 13, and 23 (Figure 1S,
Supporting Information). Although our search of the PESs of
these structures established that the Anslyn conformers were
indeed local minima, these o-(pyrrolidinylmethyl)phenylboronic
acids proved to be higher-energy conformers than in our model
compounds.
Nitrogen-Boron Distance Comparisons. As a result of the
paucity of experimental structural data for o-(N,N-dialkylami-
nomethyl)arylboronate systems,27,74 we report nitrogen-boron
distances in Tables 1S and 2S of the Supporting Information.
The single-crystal X-ray structure of the S,S-diboronic acid (S,S-
6)-L-tartaric acid complex isolated by James and co-workers27
provides a good example of an experimental structure to
compare with our calculated structure 11. All the computational
methods we employed perform quite favorably in emulating the
two experimental nitrogen-boron distances (3.43 and 3.50 Å)
reported for the S,S-diboronic acid (S,S-6)-L-tartaric acid
complex; i.e., the range of our calculated boron-nitrogen
distances for structure 11 is 3.41-3.62 Å (see Tables 1S and
2S, Supporting Information). We note that the implicit solvent
models tend to predict geometries with contracted nitrogen-boron
distances relative to the gas phase in structures 10, 14, 18, and
21.
Concluding Remarks
In the development of o-(N,N-dialkylaminomethyl)arylbor-
onate-based sensors for saccharide detection, it is critical to
understand the relative energies of NfB dative-bonded and
B-O-H · · ·N hydrogen-bonded conformers, as well as the
thermochemistry of solvent inserted forms that yield structures
involving a B · · ·OHR · · ·N linkage. The model systems (10-23)
chosen for this investigation represent a transition from the free
boronic acid in group 1 (10-13), through partial esterification
in group 2 (14-17), to full esterification in groups 3 (18-20)
and 4 (21-23); selection of these particular structures was
influenced in part by our available computational resources.
These calculations have enabled us to establish a starting-point
from which to determine the role of various nitrogen-boron
interactions in o-(N,N-dialkylaminomethyl)arylboronate-based
sensor systems. In general, these findings provide robust
thermodynamic evidence31–33 reiterating that the fluorescence
intensity of o-(N,N-dialkylaminomethyl)arylboronate based sen-
sors requires an understanding of NfB, B-O-H · · ·N, and
B · · ·OH2 · · ·N.
Although the behavior of the o-(N,N-dialkylaminomethyl)-
arylboronates model systems we investigated proved to be
complicated, several thermochemical trends have been identified:
(1) In vacuo the calculated B-O-H · · ·N intramolecular
hydrogen-bonded form of the free acid 12 (group 1) and the
partially esterified form 16 (group 2) are consistently lower in
energy than the corresponding BfN dative bonded structures
10 and 14 respectively, using MP2, PBE1PBE, and PBE1PBE-D
methodology with a variety of basis sets, but by only a few
kcal/mol (Table 1). (2) In PCM and CPCM model solutions, it
is clear that the energy difference between the B-O-H · · ·N
and BfN conformers is less than it is in the gas phase, but
which of these structures is lowest in energy is dependent on
the computational level to some extent (Tables 1 and 2), and
more computational/experimental work will be necessary to
establish unambiguously the factors that can tilt the balance in
favor of the B-O-H · · ·N or BfN conformers. (3) In vacuo,
as well as in PCM and CPCM model aqueous solutions, the
conformers in which the boron and nitrogen atoms are far
separated are significantly higher in energy than the B-O-H · · ·N
or BfN conformers for all four groups shown in Figure 4. (4)
In comparison to MP2 computations, PBE1PBE does quite well
in predicting the reaction energies used to determine the relative
stabilities of these o-(N,N-dialkylaminomethyl)arylboronates,
although relatively large basis sets appear to be essential. (5)
In vacuo and in the long-range effects of PCM and CPCM
aqueous media, the explicit hydration reactions NfB + H2O
f B · · ·OH2 · · ·N in all four groups are exothermic. (6) The
economical cc-pVDZ basis set leads to geometries consistent
with calculations performed with larger basis sets, but the
energies tend to overstabilize the hydrogen-bonded conforma-
tions. (7) The PBE1PBE functional, in conjunction with basis
sets that include diffuse functions, provides an economical
approach to studying these o-(N,N-dialkylaminomethyl)arylbo-
ronate systems. (8) The PBE1PBE-D functional, which incor-
porates the empirical dispersion correction of Grimme,58
generates thermodynamic properties closer to those of MP2 than
PBE1PBE using comparable basis sets, although more rigorous
testing is required to verify this assertion for other boron
systems; (9) the thermochemical results support the conjecture
of Wang6 and Anslyn32,33 that in protic media the B-N
interaction in o-(N,N-dialkylaminomethyl)arylboronates that
modulates the fluorescence response when the boronate is bound
N-B Interaction in o-(N,N-Dialkylaminomethyl)arylboronate J. Phys. Chem. A, Vol. 114, No. 47, 2010 12537

to saccharides involves a B · · ·OH2 · · ·N form rather than a direct
NfB dative bond.
Finally, we note that all saccharides displaying 1,2- or 1,3-
cis-diol motifs are expected to bind to monoboronic acids, and
the greatest fluorescence responses are for those saccharides
having the largest binding constants with these acids. Well
established trends for binding constants reveal that fructose has
a higher binding constant than glucose with monoboronic acids
and as such elicits a greater fluorescence response.75 The model
systems discussed in this article will help direct the future design
of boronic acid based fructose (and glucose) sensors as a result
of our identification of the relative energies of the NfB dative-
bonded and B-O-H · · ·N hydrogen-bonded conformers, as well
as the thermochemistry of solvent insertion into NfB forms
leading to a B · · ·OHR · · ·N linkage.
Acknowledgment. This research was supported in part
(J.D.L. and B.R.B.) by the Intramural Research Program of the
NIH, NHLBI. The PQS Cluster Facility at Philadelphia Uni-
versity (C.W.B.) was extensively used for the calculations
described in this manuscript. This study also utilized the high-
performance computational capabilities of the Biowulf Linux
cluster at the National Institutes of Health, Bethesda, MD (http://
biowulf.nih.gov). T.D.J. thanks the University of Bath for
support and J.S.F. thanks the University of Birmingham and
ERDF AWMII for support. J.D.L. also thanks Dr. Yihan Shao
of QChem for his helpful discussions with respect to the
incorporation of PBE1PBE-D functional.
Supporting Information Available: Table 1S and 2S:
boron-nitrogen distances for all levels of theory used in this
study. Figure 1S: Overlaid optimized geometries at the MP2/
cc-pVDZ, PBE1PBE/6-31+G(d), PBE1PBE/6-311++G(d,p),
PBE1PBE/cc-pVDZ, and PBE1PBE/aug-cc-pVDZ levels of
theory. This material is available free of charge via the Internet
at http://pubs.acs.org.
References and Notes
(1) Taylor, R. C.; Cluff, C. L. Nature 1958, 182, 390.
(2) Ho¨pfl, H. J. Organomet. Chem. 1999, 581, 129.
(3) Bosch, L. I.; Fyles, T. M.; James, T. D. Tetrahedron 2004, 60,
11175.
(4) Wiskur, S. L.; Lavigne, J. J.; Ait-Haddou, H.; Lynch, V.; Hung
Chiu, Y.; Canary, J. W.; Anslyn, E. V. Org. Lett. 2001, 3, 1311.
(5) Wulff, G. Pure Appl. Chem. 1982, 54, 2093.
(6) Franzen, S.; Ni, W.; Wang, B. J. Phys. Chem. B 2003, 107, 12942.
(7) Perdew, J. P.; Chevary, J. A.; Vosko, S. H.; Jackson, K. A.;
Pederson, M. R.; Singh, D. J.; Fiolhais, C. Phys. ReV. B 1992, 46, 6671.
(8) Klamt, A.; Schuurmann, G. J. Chem. Soc., Perkin Trans. 2 1993,
799.
(9) Andzelm, J.; Kolmel, C.; Klamt, A. J. Chem. Phys. 1995, 103, 9312.
(10) Beta, I. A.; Sorensen, C. M. J. Phys. Chem. A 2005, 109, 7850.
(11) Markovitch, O.; Agmon, N. J. Phys. Chem. A 2007, 111, 2253.
(12) James, T. D. Top. Curr. Chem. 2007, 277, 107.
(13) James, T. D.; Phillips, M. D.; Shinkai, S. Boronic Acids in
Saccharide Recognition; RSC: London, U.K., 2006.
(14) Han, F.; Chi, L. N.; Liang, X. F.; Ji, S. M.; Liu, S. S.; Zhou, F. K.;
Wu, Y. B.; Han, K. L.; Zhao, J. Z.; James, T. D. J. Org. Chem. 2009, 74,
1333.
(15) Scrafton, D. K.; Taylor, J. E.; Mahon, M. F.; Fossey, J. S.; James,
T. D. J. Org. Chem. 2008, 73, 2871.
(16) James, T. D.; Shinkai, S. Top. Curr. Chem. 2002, 218, 159.
(17) Arimori, S.; Bell, M. L.; Oh, C. S.; Frimat, K. A.; James, T. D.
J. Chem. Soc., Perkin Trans. 1 2002, 803.
(18) Arimori, S.; Bell, M. L.; Oh, C. S.; Frimat, K. A.; James, T. D.
Chem. Commun. 2001, 1836.
(19) James, T. D.; Sandanayake, K. R. A. S.; Shinkai, S. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1910.
(20) James, T. D.; Linnane, P.; Shinkai, S. Chem. Commun. 1996, 281.
(21) James, T. D.; Sandanayake, K. R. A. S.; Shinkai, S. Nature 1995,
374, 345.
(22) James, T. D.; Sandanayake, K. R. A. S.; Iguchi, R.; Shinkai, S.
J. Am. Chem. Soc. 1995, 117, 8982.
(23) James, T. D.; Sandanayake, K. R. A. S.; Shinkai, S. J. Chem. Soc.,
Chem. Commun. 1994, 477.
(24) James, T. D.; Sandanayake, K. R. A. S.; Shinkai, S. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 2207.
(25) Plumley, J. A.; Evanseck, J. D. J. Phys. Chem. A 2009, 113, 5985.
(26) Ni, W. J.; Kaur, G.; Springsteen, G.; Wang, B. H.; Franzen, S.
Bioorg. Chem. 2004, 32, 571.
(27) Zhao, J.; Davidson, M. G.; Mahon, M. F.; Kociok-Ko¨hn, G.; James,
T. D. J. Am. Chem. Soc. 2004, 126, 16179.
(28) Springsteen, G.; Wang, B. Tetrahedron 2002, 58, 5291.
(29) Bhat, K. L.; Braz, V.; Laverty, E.; Bock, C. W. J. Mol. Struct.
(THEOCHEM) 2004, 712, 9.
(30) Bhat, K. L.; Howard, N. J.; Rostami, H.; Lai, J. H.; Bock, C. W.
J. Mol. Struct. (Theochem.) 2005, 723, 147.
(31) Morrison, J. D.; Letsinger, R. L. J. Org. Chem. 1964, 29, 3405.
(32) Zhu, L.; Shabbir, S. H.; Gray, M.; Lynch, V. M.; Sorey, S.; Anslyn,
E. V. J. Am. Chem. Soc. 2006, 128, 1222.
(33) Collins, B. E.; Sorey, S.; Hargrove, A. E.; Shabbir, S. H.; Lynch,
V. M.; Anslyn, E. V. J. Org. Chem. 2009, 74, 4055.
(34) Bhat, K. L.; Hayik, S.; Corvo, J. N.; Marycz, D. M.; Bock, C. W.
J. Mol. Struct. (THEOCHEM) 2004, 673, 145.
(35) Larkin, J. D.; Bhat, K. L.; Markham, G. D.; Brooks, B. R.; Lai,
J. H.; Bock, C. W. J. Phys. Chem. A 2007, 6489.
(36) Gilbert, T. M. J. Phys. Chem. A 2004, 108, 2550.
(37) LeTourneau, H. A.; Birsch, R. E.; Korbeck, G.; Radkiewicz-
Poutsma, J. L. J. Phys. Chem. A 2005, 109, 12014.
(38) Plumley, J. A.; Evanseck, J. D. J. Chem. Theory Comput. 2008, 4,
1249.
(39) Larkin, J. D.; Markham, G. D.; Milkevitch, M.; Brooks, B. R.; Bock,
C. W. J. Phys. Chem. A 2009, 113, 11028.
(40) Møller, C.; Plesset, M. S. Pure Appl. Chem. 1934, 46, 618.
(41) Dunning, T. H. J. Chem. Phys. 1989, 90, 1007.
(42) Kendall, R. A.; Dunning, J. T. H.; Harrison, R. J. J. Chem. Phys.
1992, 96, 6796.
(43) Peterson, K. A.; Woon, D. E.; Dunning, J. T. H. J. Chem. Phys.
1994, 100, 7410.
(44) Woon, D. E.; Dunning, T. H. J. Chem. Phys. 1993, 98, 1358.
(45) Clark, T.; Chandrasekhar, J.; Spitznagel, G. W.; Schleyer, P. V.
J. Comput. Chem. 1983, 4, 294.
(46) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.;
Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Naskajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.; Jaramillo, J.;
Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.;
Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels,
A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. G.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, B.02;
Gaussian Inc., Pittsburgh, PA, U.S., 2003.
(47) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson,
G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.;
Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.;
Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.;
Nakai, H.; Vreven, T.; Montgomery, J., J. A.; Peralta, J. E.; Ogliaro, F.;
Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.;
Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.;
Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.;
Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts,
R. E.; Stratmann, O.; Yazyev, A. J.; Austin, R.; Cammi, C.; Pomelli, J. W.;
Ochterski, R.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.;
Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09;
Gaussian, Inc.: Wallingford, CT, U.S., 2009.
(48) Carpenter, J. E.; Weinhold, F. J. Mol. Struct. (THEOCHEM) 1988,
169, 41.
(49) Curtiss, L. A.; Weinhold, F. Chem. ReV. 1988, 88, 899.
(50) Foster, J. P.; Weinhold, F. J. Am. Chem. Soc. 1980, 102, 7211.
(51) Reed, A. E.; Weinstock, R. B.; Weinhold, F. J. Chem. Phys. 1985,
83, 735.
(52) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. J. Chem. Phys.
1980, 72, 650.
(53) Clark, T.; Chandrasekhar, J.; Spitznagel, G. W.; Von Rague´
Schleyer, P. J. Comput. Chem. 2004, 4, 294.
12538 J. Phys. Chem. A, Vol. 114, No. 47, 2010 Larkin et al.

(54) Li, Q.; Xue, F.; Mak, T. C. W. Inorg. Chem. 1999, 38, 4142.
(55) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV. Lett. 1997, 78,
1396.
(56) Rabuck, A. D.; Scuseria, G. E. Chem. Phys. Lett. 1999, 309, 450.
(57) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV. Lett. 1996, 77,
3865.
(58) Grimme, S. J. Comput. Chem. 2006, 27, 1787.
(59) Shao, Y.; Molnar, L. F.; Jung, Y.; Kussmann, J.; Ochsenfeld,
C.; Brown, S. T.; Gilbert, A. T. B.; Slipchenko, L. V.; Levchenko, S. V.;
O’Neill, D. P.; DiStasio, R. A.; Lochan, R. C.; Wang, T.; Beran, G. J. O.;
Besley, N. A.; Herbert, J. M.; Lin, C. Y.; Van Voorhis, T.; Chien, S. H.;
Sodt, A.; Steele, R. P.; Rassolov, V. A.; Maslen, P. E.; Korambath, P. P.;
Adamson, R. D.; Austin, B.; Baker, J.; Byrd, E. F. C.; Dachsel, H.;
Doerksen, R. J.; Dreuw, A.; Dunietz, B. D.; Dutoi, A. D.; Furlani, T. R.;
Gwaltney, S. R.; Heyden, A.; Hirata, S.; Hsu, C. P.; Kedziora, G.;
Khalliulin, R. Z.; Klunzinger, P.; Lee, A. M.; Lee, M. S.; Liang, W.;
Lotan, I.; Nair, N.; Peters, B.; Proynov, E. I.; Pieniazek, P. A.; Rhee,
Y. M.; Ritchie, J.; Rosta, E.; Sherrill, C. D.; Simmonett, A. C.; Subotnik,
J. E.; Woodcock, H. L.; Zhang, W.; Bell, A. T.; Chakraborty, A. K.;
Chipman, D. M.; Keil, F. J.; Warshel, A.; Hehre, W. J.; Schaefer, H. F.;
Kong, J.; Krylov, A. I.; Gill, P. M. W.; Head-Gordon, M. Phys. Chem.
Chem. Phys. 2006, 8, 3172.
(60) Tomasi, J.; Mennucci, B.; Cammi, R. Chem. ReV. 2005, 105, 2999.
(61) Cances, E.; Mennucci, B.; Tomasi, J. J. Chem. Phys. 1997, 107,
3032.
(62) Cossi, M.; Barone, V.; Mennucci, B.; Tomasi, J. Chem. Phys. Lett.
1998, 286, 253.
(63) Cossi, M.; Scalmani, G.; Rega, N.; Barone, V. J. Chem. Phys. 2002,
117, 43.
(64) Mennucci, B.; Cances, E.; Tomasi, J. J. Phys. Chem. B 1997, 101,
10506.
(65) Mennucci, B.; Tomasi, J. J. Chem. Phys. 1997, 106, 5151.
(66) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995.
(67) Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. J. Comput. Chem.
2003, 24, 669.
(68) Takano, Y.; Houk, K. N. J. Chem. Theory Comput. 2005, 1, 70.
(69) Castejon, H.; Wiberg, K. B. J. Am. Chem. Soc. 1999, 121, 2139.
(70) Castejon, H.; Wiberg, K. B.; Sklenak, S.; Hinz, W. J. Am. Chem.
Soc. 2001, 123, 6092.
(71) Allen, M. J.; Tozer, D. J. J. Chem. Phys. 2002, 117, 11113.
(72) Kristyan, S.; Pulay, P. Chem. Phys. Lett. 1994, 229, 175.
(73) Barone, V.; Biczysko, M.; Pavone, M. Chem. Phys. 2008, 346, 247.
(74) Bosch, L. I.; Mahon, M. F.; James, T. D. Tetrahedron Lett. 2004,
45, 2859.
(75) Lorand, J. P.; Edwards, J. O. J. Org. Chem. 1959, 24, 769.
JP1087674
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