Synthesis, structure, and two-photon absorption studies of a phosphorus-based tris hydrazone ligand (S)P[N(Me)N=CH-C₆H₃-2-OH-4-N(CH₂CH₃)₂]₃ and its metal complexes

Abstract

A phosphorus-supported multidentate ligand (S)P[N(Me)N-CH-C₆H₃-2-OH-4-N(CH ₂CH₃)₂]₃ (1) has been used to prepare mononuclear complexes LM [M = Fe (2) Co (3)] and trinuclear complexes L₂M₃ [M = Mn (4), Ni (5), Zn (6), Mg (7), Cd (8)]. In both 2 and 3 the ligand binds the metal ion in a facial coordination mode utilizing three imino nitrogen (3N) and three phenolic oxygen (3O) atoms. The molecular structures of L₂Mn₃, L₂Ni₃, L₂Zn₃, L₂Mg₃, and L₂Cd₃ (4-8) are similar; two trihydrazone ligands are involved in coordination to hold the three metal ions in a linear fashion. Each of the trishydrazone ligands behaves as a trianionic hexadentate ligand providing three imino and three phenolic oxygen atoms for coordination to the metal ions. The coordination environment around the two terminal metal ions is similar (3N, 3O) while the central metal ion has a 6O coordination environment. Third-order non-linear optical properties of these compounds as measured by their two-photon absorption (TPA) cross section reveals that while 1 does not possess obvious TPA activity, complexes 2 (3213 GM) and 4 (3516 GM) possess a large TPA cross section at 770 nm.