A synthetic strategy has been developed for bis(benzimidazole) ligands in which the two halves are different (4-11), and consequently of different basicity, which could be important for biomimicry and metal ion transport. Their coordination chemistry toward copper(II) has been studied in the solid state via X-ray crystallography. The ligands were complexed with copper(II) bromide and perchlorate salts to yield complexes of a 1:1 stoichiometry. Crystal structures have been determined and compared for [Cu(4)(NCCH3)(OH2)](ClO4)(2) (complex A, [C20H23CuN5O2](ClO4)(2), monoclinic, space group P2(1)/c, a = 10.2168(7) Angstrom, b = 30.740(2) Angstrom, c = 8.3403(6) Angstrom, beta = 105.960(2)degrees, V = 2518.4(3) Angstrom(3), Z = 4), [Cu(6)Br-2]. DMF (complex B, [C17H16Br2CuN4O]. C3H7NO, monoclinic, space group P2(1)/c, a = 8.3348(11) Angstrom, b = 18.165(2) Angstrom, c = 14.140(2) Angstrom, beta = 91.646(3)degrees, V = 2140.0(5) Angstrom(3), Z 4), [Cu(8)Br-2]. DMF . H2O (complex C, [C16H13Br2CuN5O3]. C3H7NO . H2O, monoclinic, space group P2(1)/c, a = 8.7241(10) Angstrom, b = 18.172(2) Angstrom, c = 14.506(2) Angstrom, beta = 97.376(2)degrees, V = 2280.7(4) Angstrom(3), Z = 4), [Cu(3)Br-2]. MeOH (complex D, [C16H14Br2CuN4O]. CH4O, orthorhombic, space group Pbca, a = 14.325(2) Angstrom, b = 13.919(2) Angstrom, c = 18.837(2) Angstrom, V = 3756.0(9) Angstrom(3), Z = 8), [Cu(4)Br-2]. MeOH (complex E, [C18H18Br2CuN4O]. CH4O, triclinic, space group , a = 7.3120(11) Angstrom, b = 9.9460(15) Angstrom, c = 15.189(2) Angstrom, alpha = 87.476(4)degrees, beta = 89.093(4)degrees, gamma = 68.673(3)degrees, V = 1028.0(3) Angstrom(3), Z = 2), and Cu(10)Br-2 (complex F, C16H13Br2CuN3OS, monoclinic, space group P2(1)/c, a = 7.3130(9) Angstrom, b = 15.861(2) Angstrom, c = 14.846(2) Angstrom, beta = 98.318(2)degrees, V = 1704.0(4) Angstrom(3), Z = 4). The Cu(II) complexes were found to be five;coordinate, lying between perfect square-based-pyramidal (SEP) and trigonal-bipyramidal (TBP) extremes; in each case the ligands act as tridentate donors coordinating through the pyridine-like nitrogens of the benzimidazole moieties and the ether donor atom of the linking bridge. Use of the structural index parameter (tau) for five-coordinate metal complexes indicated that all the copper(II) complexes exhibit a greater tendency toward square-based-pyramidal geometry (i.e. tau < 0.5). Comparison of the symmetrical bis(benzimidazole) complex with the other, asymmetric, complexes revealed no significant change in the geometrical parameters around the copper(II) ion consequent on introduction of asymmetry and a change of pKa within the bis(benzimidazole) fragment. The degree of hydrogen bonding, solvent of crystallization, and the nature of the anion have a greater impact on the geometrical parameters and coordination environment of the copper(II) ion. The import for biological metal coordination is considered.