Layer Geometry Modulation in Cu(II) Coordination Networks Based on Disubstituted Bis(imidazolyl)benzene Ligands

The structural chemistry of two-dimensional Cu(II) coordination networks constructed from ring-disubstituted bis(imidazolyl)benzene ligands has been investigated in order to elucidate the combined influence of ligand functionalization and counteranion identity on layer geometry, packing, and framework stability. The dimethyl-substituted ligand (bibMe2) affords three closely related layered frameworks when combined with copper(II) nitrate (UdP-8-NO3), copper(II) perchlorate (UdP-8-ClO4), or copper(II) tetrafluoroborate (UdP-8-BF4), leading to new compounds of formula [Cu(bibMe2)2(X)2]·nSolv (X = NO3, ClO4 or BF4). UdP-8-NO3 and UdP-8-ClO4 were obtained both in single crystal and powder form. On the other hand, UdP-8-BF4 could only be isolated as a powder. UdP-8-NO3 and UdP-8-ClO4 are isoreticular at the local coordination level, showing a sql topology, but display markedly different layer arrangements, stacking modes, interlayer separations, and accessible void volumes. These structural differences translate into a pronouncedly different response to external stimuli, as revealed by PXRD-based stability tests under humidity, vacuum, and variable temperature conditions. Extension to a methoxy-disubstituted ligand (bibOMe2) yields single crystals of a further two-dimensional Cu(II) network describable with a formula [Cu(bibOMe2)2(ClO4)2] (UdP-9-ClO4). This compound could only be isolated as single crystals; therefore, no further characterization was carried out.