Synthesis, crystal structures, and third-order nonlinear optical properties of a series of ferrocenyl organometallics

Three novel ferrocenyl complexes [Zn(4-PFA)₂(NO₃)₂](H₂O)(1), [Hg₂(OAc)₄(4-BPFA)₂](CH₃OH)(2), and [Cd₂(OAc)₄-(4-BPFA)₂] (3) (4-PFA = [(4-pyridylamino)carbonyl]ferrocene, 4-BPFA = 1,1′-bis[(4- pyridylamino)carbonyl]ferrocene) were prepared, and complexes 1 and 2 were structurally characterized by means of X-ray single-crystal diffraction. In complex 1, the zinc(II) atom is coordinated at a distorted tetrahedral environment by two nitrogen atoms from two 4-PFA moieties and two oxygen atoms from two nitrate anions; [Zn(4-PFA)₂(NO₃)₂] units are linked by hydrogen bonds N-H···O and H···O forming one-dimensional chains. Complex 2 is a tetranuclear macrocycle compound consisting of two 4-BPFA moieties and two Hg atoms; [Hg₂(OAc)₄(4-BPFA)₂] units form 1-D chains by hydrogen bonds N-H···O as complex 1. Some complexes with 1,1′-bisubstituted pyridine-containing ferrocene ligands have been described, but their crystal data are limited. Compound 2 is the first example of a macrocyclic pyridine-containing ferrocenyl complex. The third-order nonlinear optical (NLO) properties of 4-PFA, 4-BPFA, and complexes 1-3 were determined by Z-scan techniques. The results indicate that all the compounds exhibit strong self-focusing effect. The hyperpolarizability γ values are calculated to be in the range 1.51 × 10^-28 to 3.12 × 10^-28 esu. The y values are nearly twice as large for complexes 1-3 as for their individual ligands, showing that the optical nonlinearity of the complexes is dominated by the ligands.