Synthesis, structural characterization, EPR spectroscopy and hirshfeld surface analysis of a novel Cu2+-doped 3,14-diethyl-2,13-diaza-6,17-diazonia-tricyclo[16.4.0.07,12]docosane bis(perchlorate)

Abstract

Cyclam derivatives and their metal complexes have been found to exhibit an anti-HIV effect and stimulate the activity of stem cells from bone marrow. The strength of their binding to the CXCR4 receptor correlates with anti-HIV and stem-cell activities. Knowledge of the conformation and crystal packing of various macrocyclic metal complexes has become important in developing new effective anti-HIV drugs. The synthesis and preparation of single crystals of a new Cu2+-doped macrocyclic compound, (3,14-diethyl-2,6,13,17-tetraazatri-cyclo[16.4.0.07,12]docosane)copper(II) bis(perchlorate)–3,14-diethyl-2,13-diaza-6,17-diazoniatricyclo[16.4.0.07,12]docosane bis(perchlorate) (0.69/0.31), {[Cu-(C22H44N4)](ClO4)2}0.69.(C22H46N42+.2ClO4)0.31, is reported. Characterization by X-ray diffraction analysis shows that the asymmetric unit contains half of a centrosymmetric molecule. The macrocyclic ligand in the compound adopts the most stable trans-III conformation. The Cu—N distances of 2.015 (3) and 2.047 (3) Å are normal, but the long axial Cu—O bond of 2.795 (3) Å may be due to a combination of the Jahn–Teller effect and the strong in-plane ligand field. The crystal structure is stabilized by hydrogen bonding between secondary N—H groups, the N atoms of the macrocycle and the O atoms of the perchlorate anions. Hirshfeld surface analysis with 2D (two-dimensional) fingerprint plots indicates that the main contributions to the crystal packing are from H…H (58.0%) and H…O/O…H (41.9%) interactions. Electron paramagnetic resonance (EPR) properties are also described.