The crystal supramolecularity of metal phenanthroline complexes

The 1,10-phenanthroline (phen) ligand in metal complexes commonly forms off set face-to-face (OFF) motifs, and less frequently edge-to-face (EF) motifs . An investigation of the 335 M(phen) complexes, 159 M(phen)(2) complexes, and 33 M(phen)(3) complexes in the Cambridge Structural Database has reveal ed that in crystals these primary OFF and EF motifs combine to form concert ed motifs, and extended motifs, in a variety of ways. Stacks of phen ligand s engaging OFF motifs on both faces are very common for complexes M(phen) a nd M(phen)(2). Even more common for M(phen)(2) are zigzag chains in which e ach phen ligand links to neighbours in the chain with an OFF motif. The par allel fourfold aryl embrace (P4AE, comprised of one OFF and two EF) occurs for complexes M(phen)(2) and M(phen)(3), with some variety in geometry betw een a single OFF at one extreme to (EF)(2) at the other. This variability i n the P4AE is a consequence of the larger surface area of the phen ligand, compared with those of 2,2'-bipyridyl (bipy) ligands or phenyl groups (whic h also form this motif), and has been evaluated by calculations of the supr amolecular attractive energies. The P4AE associate further, maximising the use of phen surfaces, to form chains of P4AE, chains of P4AE . OFF, and com pact two-dimensional nets propagated by both P4AE and OFF motifs. There are examples of three-dimensional nets using these motifs. There is a notable absence of sixfold aryl embraces (6AE, comprised of concerted (EF)(6)) amon gst M(phen)(3) complexes, and a clear difference with M(bipy)(3) complexes where 6AEs are prevalent. Various M(phen)(2) and M(phen)(3) complexes pack in crystals to form tight hydrophobic domains, often as slabs, segregated f rom hydrophilic domains containing hydrogen bonding components and anions. The crystallisation and crystal packing of [Co(phen)(3)][BF4](2).H2O . EtOH , which exemplifies this pattern, are reported. The implications for crysta l engineered enantioselection by [M(phen)(3)] complexes are discussed.