Synthesis, characterization, and spontaneous resolution of chiral nickel(II) complexes with the tripod ligand tris[2-(((2-phenylimidazol-4-yl)methylidene)amino)ethyl]amine

The chiral nickel(II) complexes of a tripod-type ligand with the chemical f ormulas [Ni(H3L)](NO3)(2).MeOH (1), [Ni(H3L)](ClO4)(2).MeoH (2), and [Ni(H3 L)](C6H6COO)(2).6H(2)O (3) were synthesized and characterized (H3L = tris[2 -(((2-phenylimidazol-4-yl)methylidene)amino)ethyl]amine). The crystal struc tures of 1-3 were determined by their single-crystal X-ray analyses. 1, C37 H40N12O7Ni: orthorhombic, P2(1)2(1)2(1); a = 14.198(2) Angstrom, b = 22.422 (2) Angstrom, c = 12.019(2) Angstrom, Z = 4. 2, C37H40N10O9Cl2Ni: orthorhom bic, P2(1)2(1)2(1); a = 14.206(2) Angstrom, b = 22.735(3) Angstrom, c = 12. 696(3) Angstrom, Z = 4. 3, C50H58N10O10Ni: triclinic, P (1) over bar; a = 1 4.191(5) Angstrom, b = 16.048(4) Angstrom, c = 13.692(4) Angstrom, alpha = 115.25(2)degrees, beta = 111.07(3)degrees, gamma = 64.75(2)degrees, Z = 2. Each complex has an octahedral coordination environment for the nickel(II) ion, formed by the six nitrogen donor atoms, and is either a Delta (clockwi se) or a Lambda (anticlockwise) enantiomorph, depending on the screw arrang ement of the tripod-type ligand around the nickel(II) ion. The circular dic hroism (CD) spectrum of a powdered sample of a crystal of 1 showed a positi ve and a negative peak at 915 and 630 nm, respectively, and that of another crystal showed an enantiomeric pattern. The observation of the Cotton effe ct and the crystal structure provided evidence for spontaneous resolution o f the chiral complex molecule.