Extended structures of transition metal complexes of 6,7-dicyanodipyridoquinoxaline:: π-Stacking, weak hydrogen bonding, and CN•••π interactions

The extended structures of transition metal complexes of the phenanthroline-based ligand 6,7-dicyanodipyridoquinoxaline (dicnq) are reported, including the mixed ligand complex [{Cu(dicnq)Br}(2)H(2)btca]1.7(CH3OH), where H(2)btca = doubly deprotonated 1,2,4,5-benzenetetracarboxylic acid, which shows 1-D coordination chains that organize into a 2-D net through hydrogen bonding. [Cu(dicnq)Br-2] has square-pyramidal geometry and forms 1-D zigzagging coordination chains that pack into a 2-D herringbone motif. In complex [Ni(dicnq)(3)]Br-2 center dot(3HO)-O-2, the octahedral complex cations show unusual CN...pi interactions and form a porous 3-D structure. Both complexes [Co(dicnq)(2)Br-2] and [Cu(dicnq)(2)Br-2][Cu(dicnq)(2)Br]Br center dot(CH3CN)center dot 2(H2O) show roughly octahedral complexes that show weak C-(HN)-N-... hydrogen bonding along with pi-pi stacking interactions to form 3-D network structures such as a 3-fold interpenetrating diamondoid structure. Complex [Ag(dicnq)(2)](CF3SO3) forms zigzagging chains through pi-pi stacking interactions.