The role of C-Br‚‚‚X synthons in the structures of Cu(nbp) 2 X 2 (nbp ) n-bromopyridine; n ) 2 and 3) are investigated. A comparison of the role of these synthons in these and in the previously published (nBP) 2 CuX 4 and (nBP)X structures (nBP ) n-bromopyridinium cations; X ) Bror Cl -; n ) 2, 3, or 4) indicate that electrostatic effects, the positive charge on the bromopyridinium cation and the negative charge on the halide anion, play a major role in the strength and directionality of C-Br‚‚‚X synthons. The data indicates that the C-Br‚‚‚X synthons are stronger in the (nBP) 2 CuX 4 and (nBP)X salts compared with the Cu(nbp) 2 X 2 compounds. The supramolecular assembly of these Cu(nbp) 2 X 2 complexes is dominated by nontraditional C-Br‚‚‚X synthons and Cu‚‚‚X semicoordinate bonds. The bromine-halide distances are almost equal to the sum of their van der Waals radii (r vdW ) in Cu(3bp) 2 X 2 but less than the sum of the r vdW by ∼0.24 Å in Cu(2bp) 2 X 2 . The C-Br‚‚‚X angles are close to linear, ranging from 158.15(8)°to 167.90(8)°for Cu(3bp) 2 Cl 2 and Cu(2bp) 2 Cl 2 respectively. The Cu(2bp) 2 X 2 units form chain structures based on the C-Br‚‚‚X synthons. These chains interact via C-H‚‚‚X and π-π stacking to form the three-dimensional structure. In contrast, the chain structures in Cu(3bp) 2 X 2 compounds are based on the Cu‚‚‚X semicoordinate bond. These chains interact via C-Br‚‚‚X synthons to form the three-dimensional structure.
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