Syntheses, Structures and Nonlinear Optical Properties of Ferrocenyl Complexes with Arylethenyl Substituents

Abstract

The complexes (E)- and (Z)-Fe(η5-C5H4CHO)(η5-C5H4CH=CH−C6H4-4-NO2) [2-(E) and 2-(Z), respectively], (E)- and (Z)-Fe(η5-C5H4CHO)(η5-C5H4CH=CH−C6H4-4-CN) [3-(E) and 3-(Z), respectively], (E,E)-, (E,Z)-, and (Z,Z)-Fe(η5-C5H4CH=CHC6H4-4-NO2)2 [4-(E,E), 4-(E,Z), and 4-(Z,Z), respectively], (E,E)-, (E,Z)-, and (Z,Z)-Fe(η5-C5H4CH=CHC6H4-4-CN)2 [5-(E,E), 5-(E,Z), and 5-(Z,Z), respectively], and Fe(η5-C5H5)(η5C5H4−(E)-CH=CH−4-{(η6-C6H4)Cr(CO)3}−(E)-CH=CH−η5C5H4)Fe(η5-C5H5) (7) have been synthesized. Structural studies on 2-(E), 4-(E,Z), 5-(E,E), Fe(η5-C5H5){η5-C5H4−(E)-CH=CH−4-C6H4−(E)-CH=CH−η5-C5H4}Fe(η5-C5H5) (6) and 7 have been performed. Electrochemical studies of 2−5 reveal trends in the oxidation potentials which are consistent with the more effective conjugation of the (E) isomers, and the better electron-accepting character of NO2 than CN and of CHO than H. Powder SHG measurements by the Kurtz technique using fs pulses at the telecommunications wavelength of 1.3 μm reveal low responses for 4-(E,E), 5-(E,E), and 7. Third-order NLO measurements by Z-scan using fs pulses at 800 nm suggest an increase in |γ| on increasing the electron-acceptor strength [when proceeding from 5-(E,Z) to 4-(E,Z), CN is replaced by NO2], and on introduction of the Cr(CO)3 unit, when proceeding from 6 to 7.