Influence of para substituents in controlling photophysical behavior and different non-covalent weak interactions in zinc complexes of a phenol based "end-off" compartmental ligand

Three dinuclear zinc(II) complexes with "end-off" compartmental ligands, namely 2,6-bis(N-ethylmorpholine-iminomethyl)-4-R-phenol (I: R = -CH3, Cl, tBu) were synthesized with the aim of exploring the role of the para substituent present in the ligand backbone in controlling the structural diversity, photophys. properties and different weak interactions of the complexes. The complexes are [Zn2L1(CH3CO2)2]1/2[Zn(NCS)4].3/2H2O (1), [Zn2L2(CH3CO2)2]1/2[Zn(NCS)4] (2), and [Zn2L3(CH3CO2)2]1/2[Zn(NCS)4] (3),. All three species, with the general formula 2[Zn2L(CH3COO)2][Zn(NCS)4], show the complex anion Zn(NCS)42- as a common structural feature decisive for crystn. All of them possess several noncovalent weak interactions where the nature of the "R'' group plays an essential role as exposed by DFT study. Besides exhibiting fluorescence behavior, the complexes also show para substitution controlled phosphorescence both at room and low temp. Anisotropy studies suggest the existence of complexes 2 and 3 as dimers in soln. The origins of the unusual room temp. phosphorescence and fluorescence behavior of the complexes were rationalized in the light of theor. calcns. [on SciFinder(R)]