1-D Polymeric divalent metal m-ferrocenylbenzoates: Structures, NLO and electrochemical properties

Three 1-D metal–organic polymers containing m-ferrocenylbenzoate components: {[Pb(μ2-η2-OOCH4C6Fc)2] · (CH3OH)2}n (1), [Zn(OOCH4C6Fc)2(bpe)]n (2) and [Mn(η2-OOCH4C6Fc)2(4,4′-bpy)]n (3) were synthesized and structurally characterized. In polymer 1, each m-FcC6H4COO− anion adopts a tridentate fashion, bridging the central Pb(II) ions to form a 1-D chain. Polymers 2 and 3 give similar zigzag chain structures. Their third-order NLO properties were investigated with 532 nm laser pulses of 8 ns duration by Z-scan experiment in DMF solution. All of the polymers exhibit good NLO refractive properties with self-focusing behaviors. The third-order NLO refractive indexes n2 are 2.44 × 10−11 esu for 1, 2.33 × 10−11 esu for 2, and 2.10 × 10−11 esu for 3, respectively. Through quantum chemistry calculations, we conclude that the nonlinear refractive behaviors of the three polymers mainly come of the ferrocenyl units and organic adjuvant ligands; Mn(II) ions and Pb(II) ions have also some influence on NLO properties. The solution-state differential pulse voltammetrys indicate that the half-wave potential of the ferrocenyl moiety in 3 has slightly higher value than those of 1 and 2. This may be because the HOMO orbitals in 1 and 2 are located in the m-FcC6H4COO− groups, while in 3 the HOMO orbital is located in the m-FcC6H4COO− and Mn(II)groups, the charge transitions of the metal cores may play an important role in the change of the Fe(II)/Fe(III) oxidation potential of 3, so the Fe(II) centers of 1 and 2 are more easily oxidized to Fe(III) centers than that of 3.