X-ray structure and spectroscopy of novel trans-[Ni(L)(NO(3))(2)] and [Ni(L)](ClO(4))(2)·2H(2)O complexes

Abstract

Ni(L)(NO(3))(2) (complex 1) and [Ni(L)](ClO(4))(2)·2H(2)O (complex 2) [L=3,14-diethyl-2,6,13,17-tetraazatricyclo(16.4.0.0(7,12))docosane] have been prepared and structurally characterized by single-crystal X-ray diffraction at 200K. For these constrained macrocycle complexes, nickel(II) exists in a distorted octahedral environment with the four nitrogen atoms of the macrocyclic ligands and two oxygen atoms from nitrate in axial positions in complex 1. The macrocyclic ligand in complex 1 adopts the most stable trans-III conformation. The Ni-N distances in both the complex 1 (2.094(4)-2.051(4)Å) and complex 2 (2.042(8)-1.996(7)Å), are typical but the axial ligands are coordinating, with NiO bond length, 2.198(3)Å for complex 1. The complex 2 adopts square planner geometry around the Ni(II) with four nitrogen atoms from macrocyclic ligand. The crystals are stabilized in a 3-D network by intra and intermolecular hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms and nitrate in 1, and intermolecular hydrogen bonds are formed by perchlorate and NH groups in 2. The electronic absorption, IR and PL spectral properties are also discussed.

Keywords: Crystal structure; Macrocyclic ligand; Nickel(II); Spectroscopic properties; trans-III Conformation.