Hybrid Molecular-Based Magnets Containing Organic NLO Chromophores:  A Search toward an Interplay between Magnetic and NLO Behavior

Abstract

A new hybrid molecular-based ferromagnet of formula [(dmaph)PPh 3 ][MnCr(ox) 3 ], where [(dmaph)PPh 3 ] + stands for the (4-dimethylaminophenyl)triphenylphosphonium cation (ox 2 - being the oxalate anion), has been synthesized. It crystallizes in the monoclinic P 2 1 space group, with lattice parameters a = 13.954(2) Å, b = 16.297(2) Å, c = 14.323(2) Å, and β = 99.27(1)°. Refinement based on F o 2 yields R = 0.072 and wR 2 = 0.156. The compound exhibits a ferromagnetic interaction between Cr 3+ and Mn 2+, with a long-range magnetic ordering at T C = 4.5 K. The hyperpolarizability ( β ) of the cation is calculated within the framework of the INDO/SOS-based method, which indicates a β value comparable to that of p -nitroaniline for an absorption maximum at 306 nm ( ε max = 28 500 M - 1 cm - 1 ). This result is consistent with the observation of a SHG efficiency 4 times that of urea for the parent [(dmaph)PPh 3 ]Br salt, at 1.907 μm. The non-centrosymmetric [(dmaph)PPh 3 ][Mn II Cr III (ox) 3 ] derivative is used as a model compound for an investigation of the potential effect of a ferromagnetic ordering on the bulk NLO response of hybrid materials made of NLO cations inserted between magnetic anionic layers.