Anion-controlled formation of silver(I) complexes of a hexaazamacrocyclic Schiff base: Synthesis, structures and electrochemistry

Abstract

Six silver(I) complexes of a macrocyclic Schiff Base (L) with different counter anions have been prepared and structurally characterized, where L is a hexaazamacrocyclic Schiff Base derived from the [2 + 2] condensation of terephthalaldehyde and 3-azapentane-1, 5-diamine. [Ag2L(NO3)(2)] (1) crystallizes in the triclinic space group P (1) over bar, with a = 7.705(7), b = 7.926(5), c = 12.06(1) Angstrom, alpha = 90.33(1), beta = 95.13(1), gamma = 104.07(1)degrees, V = 711(1) Angstrom(3) and Z = 1. [Ag2L(NO3)(2)] (2) crystallizes in the monoclinic P2(1)/n, with a = 7.714(3), b = 14.491(7), c = 11.821(6) Angstrom, beta = 98.99(1)degrees, V = 1305(1) Angstrom(3) and Z = 2. [Ag3L2(NO3)(2)] (ClO4) (3) crystallizes in the monoclinic space group C2/m, with a = 14.950(6), b = 13.258 (3), c = 27.399(16) Angstrom, beta = 109.15(1)degrees, V = 2589(2) Angstrom(3); and Z = 2. [Ag2L2](PF6)(2) (4) crystallizes in the monoclinic space group P2(1)/n, with a = 10.066(3), b = 9.846(5), c=27.40(2) Angstrom, beta = 92.81(8)degrees, V = 1712(2) Angstrom(3) and Z = 4. [Ag4L(MeCH(OH)CO2)(4)] (5) crystallizes in the monoclinic P2(1)/c, with a = 13.851(9), b = 8.043(3), c = 19.65 (1) Angstrom, beta = 107.73(2)degrees, V = 2085(2) Angstrom(3) and Z = 2. [Ag4L(PhCO2)(4)](n). nAg(2)(PhCO2)(2)(6) crystallizes in the triclinic P (1) over bar, with a = 10.896(9), b = 10.990(3), c = 13.25(1) Angstrom, alpha = 75.88(1), beta = 87.60(1), gamma = 82.91(1)degrees, V = 1527(2) Angstrom(3) and Z = 3. 1 and 2 are a pair of isomers crystallized in the triclinic and monoclinic forms with the nitrate groups acting in the bidentate chelate and monodentate modes, respectively. 3 has a discrete trinuclear [Ag-3 L-2(NO3)(2)](+) cation, in which the central metal atom is ligated by three nitrogen atoms from one L ligand and one amine nitrogen atom from the other L ligand, while at each side, the metal atom is coordinated by three nitrogen atoms from one L ligand and one nitrate oxygen atom. In 4, a pair of silver(I) atoms are wrapped by a pair of L ligands to form a dimeric cation with each metal atom being coordinated by three nitrogen atoms from one L ligand and one amine nitrogen atom from the other L ligand. 5 is a tetranuclear complex, a pair of metal atoms bridged by a mu(2)-lactate group are ligated in a triaza site with one metal atom linked to two nitrogen atoms and the other metal atom to one nitrogen atom and one monodentate lactate group. The crystal. structure of 6 comprises infinite one-dimensional [Ag4L(PhCO2)(4)](n) chains and the discrete dimeric Ag-2(PhCO2)(2) species. Each L ligand binds two inversely-related silver(I) atoms, while each of the two metal atoms is bridged by a single mu(2)-benzoate group to a bis(mu(2)-benzoate) disilver(I) core, resulting in the polymeric chain. The discrete dimeric Ag-2(FhCO(2))(2) species are inserted into the cavities constructed by the polymeric chains in 6, and interact with the chains through metal-oxygen contacts and pi-pi stacking interaction. The redox properties of the six compounds have also been investigated by cyclic voltammetry