Extended Structures of Transition Metal Complexes of 6,7-Dicyanodipyridoquinoxaline: π-Stacking, Weak Hydrogen Bonding, and CN···π Interactions

Abstract

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}2H2btca]1.7(CH3OH), where H2btca = 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)Br2] has square-pyramidal geometry and forms 1-D zigzagging coordination chains that pack into a 2-D herringbone motif. In complex [Ni(dicnq)3]Br2·3H2O, the octahedral complex cations show unusual CN···π interactions and form a porous 3-D structure. Both complexes [Co(dicnq)2Br2] and [Cu(dicnq)2Br2][Cu(dicnq)2Br]Br·(CH3CN)·2(H2O) show roughly octahedral complexes that show weak C−H···N hydrogen bonding along with π−π 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 π−π stacking interactions.