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A series of new acetylide complexes of the type [Fe(eta(5)-C5H5)(Pboolean ANDP)(p-Cequivalent toCC(6)H(4)R)] (Pboolean ANDP = DPPE (=1,2-bis(diphenylphosphino)ethane), (R)-PROPHOS (=(R)-(+)-1,2-bis(diphenylphosphino)propane), R = NO2, C6H4NO2, (Z)-C(H) C(H)C6H4NO2, (E)-C(H)=C(H)C6H4NO2) have been synthesized by halide abstraction from the precursors [Fe(eta(5)-C5H5)(Pboolean ANDP)(1)] and fully characterized. Quadratic hyperpolarizabilities (beta) for the complexes have been determined by hyper-Rayleigh scattering at 1064 nm. The influence on the nonlinear response of acetylide chain length in proceeding from 4-nitrophenylethynyl to 4-nitrobiphenylethynyl and 4-nitro(E)-stibenylethynyl has been studied, revealing values of the first hyperpolarizabilities among the highest reported for organometallic molecular materials. Comparisons on the nonlinear efficiencies are drawn with the related well-known families of compounds [Ru(eta(5)-C5H5)(PR3)(2)(P-Cequivalent toC-(aryl)-NO2)] and [Fe(eta(5)-C6H5)(Pboolean ANDP)(P-Nequivalent toC-(aryl)-NO2)](+), Cubic hyperpolarizabilities (gamma) determined by Z-scan at 800 nm are consistent with an increase in) upon replacing Ru by the more easily oxidizable Fe and upon chain-lengthening the delocalizable pi-bridging unit (proceeding from 4-C6H4 to (E)-4,4'-C6H4CH=CHC6H4). X-ray C5H5)(DPPE)(P-Cequivalent toCC(6)H(4)NO(2))] and [Fe(eta(5)-crystallographic structures of complexes [Fe(eta(5)-C5H5)DPPE)((E)-p-Cequivalent toCC(6)H(4)C(H)=C(H)C6H4NO2)] were studied in order to investigate the existence of T-back-donation suggested by spectroscopic and electrochemical data. Crystal packing was analyzed with the aim of assessing the alignment of the molecules in the lattice and hence suggesting the magnitude of NLO properties at the macroscopic level.

New binary and ternary solid solutions formed by p-chlorobenzyl alcohol (p-ClBA), p-bromobenzyl alcohol (p-BrBA) and their quasi-isostructural compound p-methylbenzyl alcohol (p-MeBA) have been prepared and characterized by DSC and powder X-ray diffraction. The binary and ternary solid solutions were synthesized by co-melting of p-MeBA/p-ClBA, p-MeBA/p-BrBA and p-ClBA/p-BrBA and by co-melting of p-MeBA/p-ClBA/p-BrBA in various molar ratios. By varying the relative concentrations, it has been possible to observe the consequent variations of the melting points of the solid solutions. For the binary 1 : 1 p-MeBA/p-BrBA and p-ClBA/p-BrBA compounds, single crystals were grown from solution and their structures were investigated by X-ray diffraction.

Two co-crystals of melatonin with piperazine and (1,4-diazabicyclo[2.2.2]octane), DABCO, and a hydrated ionic co-crystal with CaCl2 were obtained directly in the solid-state via kneading of the solid mixtures with a few drops of ethanol. The structure of the DABCO co-crystal, mel2·DABCO, was determined by single crystal X-ray diffraction, while those of the piperazine co-crystal, mel2·pip, isomorphous with the DABCO one, and the ionic co-crystal, mel2·CaCl2·2H2O, were determined from powder data. In the case of the ionic co-crystal with CaCl2, solubility measurements indicate that melatonin solubility in water increases by an order of magnitude with respect to the pure substance.