Influences of changes in multitopic tris(pyrazolyl)methane ligand topology on silver(I) supramolecular structures

Abstract

The reactions between silver tetrafluoroborate and the ligands 1,2,4,5-C6H2[CH2OCH2C (pz)3]4 (L1, pz = pyrazolyl ring), o-C6H4[CH2OCH2C (pz)3]2 (L2), and m-C6H4[CH2OCH2C (pz)3]2 (L3) yield coordination polymers of the formula {C6H6-n[CH2OCH2C (pz)3]n(AgBF4)m}∞ (n = 4, m = 2, 1; n = 2, ortho substitution, m = 1, 2; meta substitution, m = 2, 3). In the solid state, L2 molecules dimerize by a pair of C-H⋯π interactions, forming an arrangement that resembles the tetratopic ligand L1. In the solid-state structure of 1, each silver atom is κ2-bonded to two tris(pyrazolyl)methane units from different ligands with the overall structure a polymer made up from 32-atom macrocyclic rings formed by bonding tris(pyrazolyl)methane groups from nonadjacent positions on the central arene rings to the same two silver atoms. In 2, each silver is bonded to two tris(pyrazolyl)methane units in the same κ2-κ2 fashion as with 1, forming a polymer chain. The chains are organized into dimeric units by strong face-to-face π-π stacking between the central arene rings making bitopic L2 act as half of tetratopic L1. The chains in both structures are organized by weak C-H⋯F hydrogen bonds and π-π stacking interactions into very similar 3D supramolecular architectures. The structure of 3 contains three types of silvers with the overall 3D supramolecular sinusoidal structure comprised of 32-atom macrocycles. Infrared studies confirm the importance of the noncovalent interactions. Calculations at the DFT (B3LYP/6-31G*) level of theory have been carried out on L2 and also support C-H⋯π interactions. Electrospray mass spectral data collected from acetone or acetonitrile show the presence of aggregated species such as [(L)Ag2(BF4)]+ and [(L)Ag2]2+, despite the fact that 1H NMR spectra of all compounds show that acetonitrile completely displaces the ligand whereas acetone does not.