Crystal structures of zinc(II) coordination complexes with iso-quinoline -oxide.

The reaction of one equivalent of zinc(II) halide salts with two equivalents of iso-quinoline -oxide (iQNO; CHNO) in methanol yields compounds of the general formula [Zn (iQNO)], with = Cl (), Br () and I (). However, starting with zinc(II) perchlorate or nitrate leads to the formation of complex ions with the compositions Zn(iQNO) for = ClO (), and Zn(iQNO)(HO) for = NO (). Complexes (), () and (), namely di-chlorido-bis-(iso-quinoline -oxide-κ)zinc(II) [ZnCl(CHNO)], di-bromido-bis-(iso-quinoline -oxide-κ)zinc(II) [ZnBr(CHNO)], and di-iodido-bis-(iso-quinoline -oxide-κ)zinc(II) [ZnI(CHNO)], each exhibit a distorted tetra-hedral coordination geometry around the zinc(II) ion coordinated by two iQNO ligands bound through the oxygen atom and two halide ions. The zinc ion lies on a crystallographic twofold axis in the bromo complex. The -Zn- bond angles are approximately 15-17° larger than the O-Zn-O bond angles resulting in the observed tetra-hedral distortion. In complex (), hexa-kis-(iso-quinoline -oxide-κ)zinc(II) bis-(perchlorate), Zn(CHNO), the zinc(II) ion occupies a special position with 3 site symmetry and is octa-hedrally coordinated by six iQNO ligands, albeit with slight distortions evidenced by a spread of bond angles from 85.82 (4) to 94.18 (4)°. The chlorine atom of the perchlorate anion lies on a crystallographic threefold axis. Finally, complex () crystallizes with a pseudo-octa-hedral geometry; penta-aqua-(iso-quinoline -oxide-κ)zinc(II) dinitrate-iso-quinoline -oxide (1/2), Zn(CHNO)(HO)·2(CHNO). The nitrate ions and non-coordin-ated iQNO mol-ecules engage in π-stacking and hydrogen-bonding inter-actions with the coordinated water mol-ecules. The iQNO-Zn-O equatorial bond angles range from 88.98 (9) to 94.90 (9)°, with the largest deviation from a perfect octa-hedral angle attributed to the influence of a weak C-H⋯O (from water) inter-action (2.287 Å) involving the bound iQNO ligand.