The monofunctionalized 1,4,7-triazacyclononane derivatives 1,4,7-triazacyclononane-N-acetate(L(1)) and N-(2-hydroxybenzyl)-1,4,7-triazacyclononane (HL(2)) and their complexes with vanadium(IV)/(V). Localized and delocalized electronic structures in compounds containing the mixed valent [OVIV-O-(VO)-O-V]3(+) core

The synthesis of the tetradentate pendant arm macrocycles 1,4,7-triazacyclononane-N-acetate (L(1)) and N-(2-hydroxybenzyl)-1,4,7-triazacyclononane (HL(2)) and their coordination chemistry with vanadium(IV) and (V) are reported. The following mononuclear species have been prepared and characterized by UV-Vis, IR spectroscopy: [L(I)V(IV)O(NCS)] (1), [L(1)VO(2)]. H2O (2), [L(2)VO(NCS)] (3), [L(2)VO(NCs)]Cl (4), and [L(2)VO(2)] (5). In addition, the dinuclear, mixed valent complexes [L(2)(1)V(2)O(3)]Br (6), [L(2)(2)V(2)O(3)] (ClO4). 0.5acetone (7), and the homovalent complex [L(2)(2)V(2)O(3)] (ClO4)(2) (8) have been synthesized. Complexes 2, 3, 6 and 7 have been characterized by single crystal X-ray crystallography. Crystal data: 2, space group P2(1)c, a = 9.944(4), b = 6.701(3), c = 18.207(8) Angstrom, beta = 102.88(3)degrees, V = 1182.7 Angstrom(3), Z=4, D-calc = 1.51 g cm(-3), R = 0.049 based on 4760 reflections; 3, space group Pbca, a = 11.003(6), 6 = 14.295(7), c = 20.21(1) Angstrom, V = 3178.8 Angstrom(3), Z=8, D-calc= 1,50 g cm(-3), R = 0.057 based on 1049 reflections; 6, space group Pbcn, a = 12.922(3), b = 13.852(3), c = 12.739(3) Angstrom, V = 2280.3 Angstrom(3), Z=4, D-calc = 1,75 g cm(-3), R = 0.047 based on 1172 reflections; 7, space group C2/c, a = 23.553(9), b = 13.497(5), c = 20.951(8) Angstrom, beta = 90.03(3)degrees, V = 6660.2 Angstrom(3), Z=8, D-calc = 1.49 g cm(-3), R = 0.053 based on 3698 reflections. Complexes 6 and 7 are mixed valent V(IV)/(V) complexes containing the [OV-O-VO](3+) core. In the solid state 6 belongs to class III (delocalized) and 7 to class I (localized) according to the Robin and Day classification of mixed valent compounds. A rationale for these differing electronic structures is given.