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 P1, with a = 7.705(7), b = 7.926(5), c = 12.06(1) Å, α = 90.33(1), β = 95.13(1), γ = 104.07(1)°, V = 711(1) Å3 and Z = 1. [Ag2L(NO3)2] (2) crystallizes in the monoclinic P21/n, with a = 7.714(3), b = 14.491(7), c = 11.821(6) Å, β = 98.99(1)°, V = 1305(1) Å3 and Z = 2. [Ag3L2(NO3)2] (C1O4) (3) crystallizes in the monoclinic space group C2/m, with a = 14.950(6), b = 13.258 (3), c = 27.399(16) Å, β = 109.15(1)°, V = 2589(2) Å3; and Z = 2. [Ag2L2](PF6)2 (4) crystallizes in the monoclinic space group P21/n, with a = 10.066(3), b = 9.846(5), c = 27.40(2) Å, β = 92.81(8)°, V = 1712(2) Å3 and Z = 4. [Ag4L(MeCH(OH)CO2)4] (5) crystallizes in the monoclinic P21/c, with a = 13.851(9), b = 8.043(3), c = 19.65 (1) Å, β = 107.73(2)°, V = 2085(2) Å3 and Z = 2. [Ag4L(Ph-CO2) n ·nAg2(PhCO2)2(6) crystallizes in the triclinic P 1, with a = 10.896(9), b = 10.990(3), c = 13.25(1) Å, α = 75.88(1), β = 87.60(1), γ = 82.91(1)°, V= 1527(2) Å3 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 [Ag3 L2(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 μ2-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 [Ag2L(PhCO2)4] n chains and the discrete dimeric Ag2(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 μ2-benzoate group to a bis(μ2-benzoate) disilver(I) core, resulting in the polymeric chain. The discrete dimeric Ag2(PhCO2)2 species are inserted into the cavities constructed by the polymeric chains in 6, and interact with the chains through metaloxygen contacts and π-π stacking interaction. The redox properties of the six compounds have also been investigated by cyclic voltammetry.