A series of complexes trans-[FMo(N=NCHL)(dppe) 2 ][BF 4 ] {L = (bi)thienyl or arylthienyl}, were synthesized and fully characterized by 1 H, 13 C, 31 P NMR, IR and UV/Vis spectroscopy. The electronic spectra and electrochemical behavior of the complexes were investigated. The electronic absorption spectra of these complexes display a broad low-energy band in the visible region attributable to metal-to-ligand charge-

The crystal structure and non-linear optical properties of L-alaninium perrhenate, C3H8NO2+ ReO4 −, are reported. The protonated amino acid and the perrhenate anion have their usual geometries. The three-dimensional hydrogen-bonded network can be seen as a stacking of layers parallel to the (100) planes. Each layer is formed by chains of alternating positive and negative ions along the b and c axes. Hydrogen bonding of adjacent layers forms alternating chains along the a axis. A high damage threshold and a second-harmonic generation efficiency three times that of KDP make this new material potentially useful in non-linear optics.

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C12H16K1.67O15Rb0.33, orthorhombic, P212121 (no. 19), a = 7.721(1) Å, b = 7.895(2) Å, c = 29.914(3) Å, V = 1823.6 Å 3 , Z = 4, Rgt(F) = 0.061, wRref(F 2 ) = 0.147, T = 293 K. Source of materialSingle crystals of the title compound have been grown from a saturated equimolar aqueous solution of potassium and rubidium hydroxide and L-malic acid by a controlled solvent evaporation method. A small single crystal of fair quality was selected and used for X-ray data collection. Experimental detailsAll hydrogen atoms were refined as riding with isotropic displacement parameters constrained to those of the parent atoms. Appropriate AFIX instructions with SHELXL-97 [1] defaults were used to implement the latter restraints. The final structure was examined with PLATON [2] showing that there are no solvent-accessible voids in the crystal structure. DiscussionL-malic acid (C4H6O5), one of the simplest dicarboxylic acids, is a suitable building block in crystal engineering, being used to create two dimensional anionic networks held together by hydrogen bonds [3,4]. Metal dicarboxylates are also known to form structures with varying dimensionalities, e.g., chains or layers, linked by the dicarboxylate ions [5]. This work is part of a project aiming at synthesizing and investigating the structure and physical properties of new L-malate salts. A thermal analysis of the title compound was performed on a differential scanning calorimeter in the temperature range 270 K 470 K. No phase transitions were observed up to the fusion temperature (appr. 425 K). The title compound shows a second harmonic generation with an effective second order susceptibility estimated to be 0.50 that of potassium dihydrogen phosphate [6]. The present compound is isostructural with the reported bis(potassium hydrogen L-malate) · malic acid [7]; however, the space group attributed to that structure is incompatible with preliminary measurements of the pyroelectric effect in the compound [6]. Attempts are underway to grow good quality crystals of the material in order to clarify the true symmetry of its crystal structure.The main carbon skeletons of the independent hydrogen-L-malate anions and L-malic acid molecules are in anti conformation (figure, top). The cations show an eightfold coordination to oxygen atoms of the organic molecules and form zig-zag chains along the a axis. Two neighboring cations along each chain are coordinated to sets of three oxygen atoms. The remaining two coordination O atoms connect each cation to neighboring chains of organic molecules. The crystal structure can be seen as an almost layered 3D network in which ac slabs are bridged by organic molecules through hydrogen bonding and coordination to the cations lying in the slabs (figure, bottom). In these ac planes chains of head-to-tail hydrogen-L-malate anions alternate with neutral L-malic acid molecules and zigzag chains of cations. The present material can be described as having an open framework structure with channels parallel to [100]. The rubidium cations substitut...

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