Synthesis and characterization of dodecahedral cerium(IV) and gadolinium(III) complexes with a tetradentate Schiff Base

Abstract

Reactions of CeCl < inf > 3 < /inf > 6H < inf > 2 < /inf > O and Gd(NO < inf > 3 < /inf > ) < inf > 3 < /inf > 5H < inf > 2 < /inf > O with biacetyl bis(benzoylhydrazone) (H < inf > 2 < /inf > babh) and KOH in 1:2:2 mole ratio in methanol afford the complexes [Ce(babh) < inf > 2 < /inf > ] (1) and [Gd(babh)(Hbabh)]H < inf > 2 < /inf > O (2H < inf > 2 < /inf > O), respectively in good yields. Characterization of the complexes has been performed with the help of elemental analysis, magnetic susceptibility, spectroscopic (IR, UV-Vis, EPR and NMR) and X-ray crystallographic measurements. 1 is diamagnetic and NMR active, while 2H < inf > 2 < /inf > O is paramagnetic (μ < inf > eff < /inf > = 8.03 μ < inf > B < /inf > at 300 K) and EPR active. The complexes crystallize as 1CH < inf > 2 < /inf > Cl < inf > 2 < /inf > and 2H < inf > 2 < /inf > O. X-ray structures show that the metal centre in each of 1 and 2 is in a distorted dodecahedral N < inf > 4 < /inf > O < inf > 4 < /inf > coordination sphere assembled by two meridionally spanning ONNO-donor ligands. Self-assembly of 1CH < inf > 2 < /inf > Cl < inf > 2 < /inf > via intermolecular C-H⋯N and C-H⋯Cl hydrogen bonds and π- π interactions provides one-dimensional 'ladder' type structure. On the other hand, 2H < inf > 2 < /inf > O assembles into a two-dimensional 'sheet' like network through intermolecular N-H⋯O and O-H⋯N hydrogen bonds. [Figure not available: see fulltext.]