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.

Graphical abstractThree 1-D m-ferrocenylbenzoate metal polymers: {[Pb(μ2-η2-OOCH4C6Fc)2] · (CH3OH)2}n (1), [Zn(OOCH4C6Fc)2(bpe)]n (2) and [Mn(η2-OCH4C6Fc)2(4,4′-bpy)]n (3) were synthesized and structurally characterized. By quantum chemistry calculation we elucidate the possible reason for their electrochemical behaviors and confirm the nonlinear refractive behaviors of the three polymers mainly come of the ferrocenyl ligands and organic adjuvant ligands; Mn(II) ions and Pb(II) ions have also some influence on NLO properties.Figure optionsDownload full-size imageDownload as PowerPoint slide