TDDFT study of the nonlinear optical properties of the rich d-electron molecular system – iridium/rhodium cluster: the effect of phosphaferrocene

Abstract

A series of iridium carbonyl clusters substituted with phosphaferrocene, namely [{M(η⁵-C₅H₅)}{Fe(η⁵-L₅)(η ⁵⁻C₅H₅)}] (M = Ir, L = P I-1; M = Rh, L = As I-2), [{Ir₄(CO)₁₀} _n {Fe(η⁵-P _x C_{5− x} Me_{5− x} )(η⁵⁻C₅H₅)}] (n = 1, x = 3 II-1, 1 II-2, 5 II-3; n = 2, x = 3 III-3), [Ir₄(CO)₁₀{Fe[η⁵-P₃C₂ ](η⁵⁻C₅H₅)}Ir₄(CO)₁₁] (III-1) and [Ir₄H(CO)₁₀{Fe[η⁵-P₃C(CMe₂CH₂)CBu^t](η⁵⁻C₅H₅)}Ir₄(CO)₁₁] (III-2), have been studied using the time-dependent density functional theory method (TDDFT), focusing on the electronic and nonlinear optical (NLO) properties. The calculated results suggest that their first hyperpolarizabilities are much larger than most iridium clusters coordinated by organic ligands (about 10 times larger on average), and even larger than some ferrocene derivatives coordinated by typical π-conjugated organic ligands. We expand the orbital decomposition scheme proposed by Baerends et al. and apply it to the analysis of the NLO nature of the clusters. The charge-transfer processes between the d orbitals of iron and iridium through phospha-cyclopentadienyl are assigned to the second-order NLO response mechanism.

Keywords:

• TDDFT
• phosphaferrocene
• nonlinear optical
• orbital decomposition scheme

Acknowledgements

The authors acknowledge financial support from the ‘973’ program (207CB307) and the National Science Foundation of China (205073114). We also thank the Supercomputing Center of CNIC for computer resources.