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 O−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
γ 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.