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 2being the oxalate anion), has been synthesized. It crystallizes in the monoclinic P2 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 pnitroaniline for an absorption maximum at 306 nm ( 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.

Synthesis, Crystal Structure and Thermal Behavior of a 3-D Barium(II)/Iron(III)-Oxalate Polymer

“…Yellow good crystals were isolated from the filtrate with good yield. Elemental and full X-ray structure analyses converge to support the general formulation of 1 as {Ba 6 …”

“…Compound 1 is a 3-D polymeric structure with oxalate anions and water molecules bridging Ba 2+ and Fe 3+ ions. This compound is isotructural with its chromium analog {Ba 6 (H 2 O) 17 [Cr(C 2 O 4 ) 3 ] 4 }•7H 2 O characterized earlier [12]. It seems relevant, therefore, to compare the structural features of 1 with those of the chromium analog.…”

“…Compounds of interest in this context include optically active systems [3] [4], polymeric microporous open frameworks [5] and, most importantly, molecular magnets [3] [4] [6]- [8]. In this respect, the tris(oxalato)metalate(III) anions are suitable for building multifunctional properties in a molecular lattice [9]- [11].…”

“…Following the strategy of utilizing transition metals with versatile multidentate ligands like oxalate dianion, we recently synthesized the first 3-D polymeric salt, {Ba 6 (H 2 O) 17 . This compound has proven to be a useful precursor for the synthesis of highly versatile complex salts with the unprecedented potential of accumulating within a single system a whole set of relevant functionalities, such as nanoscale structural features, extended hydrogen bonding, magnetic interactions [13]- [15].…”

“…In order to extend this family of barium(II)/metal(III)-oxalate complex salts, we now describe the synthesis, crystal structure, and thermal behavior of the new salt, {Ba 6 (H 2 O) 17 [Fe(C 2 O 4 ) 3 ] 4 }•7H 2 O, which turns out to be the iron(III) analog of the previously well-characterized barium(II)/chromium(III)-oxalate polymer [12], where chromium(III) ions are replaced by iron(III) ions.…”