Correlation between structural studies and third order NLO properties of selected new quinolinium semi-organic compounds

New quinolinium semi-organic compounds of formula ( C 9 H 8 N ) 2 + · SO 4 2 - , H 2 O (I) (bis-quinolinium sulphate monohydrate) and ( C 9 H 8 N ) + · NO 3 - (II) (quinolinium nitrate) have been synthesized and characterized by UV–Vis absorption spectroscopy, nonlinear optical (NLO) measurements and by single crystal X-ray diffraction. The third order nonlinear optical properties of (I) and (II) were investigated using two methods: the degenerate four wave mixing technique (DFWM) performed in solution at λ = 532 nm and the third-harmonic generation (THG) measurements carried out on thin films at λ = 1064 nm. The NLO measurements showed that compound (I) presents better nonlinear optical properties compared to compound (II). To understand further the optical behaviour of (I) and (II), the crystal structures of both compounds were determined from accurate single crystal X-ray diffraction measurements performed at 100 K. The crystallographic studies revealed the key role of the intermolecular interactions and the molecular arrangements in the enhancement of the NLO properties

Comparison of CCD, CMOS and Hybrid Pixel x-ray detectors: detection principle and data quality

International audienceWe compare, from a crystallographic point of view, the data quality obtained using laboratory x-ray diffractometers equipped with a Molybdenum micro-source using different detector types: CCD, CMOS and XPAD hybrid pixel. First we give an overview of the working principle of these different detector types with a focus on their principal differences and their impact on the data quality. Then, using the example of an organic crystal, a comparison between the detector systems concerning the raw data statistics, the refinement agreement factors, the deformation electron density maps, and the residual density after multipolar refinement is presented. It is found that the data quality obtained with the XPAD detector is the best, even though the detection efficiency at the Mo energy (17.5 keV) is only 37% due to the Si-sensor layer thickness of 300 mu m. Finally, we discuss the latest x-ray detector developments with an emphasis on the sensor material, where replacing Si by another material such as GaAs would yield detection efficiencies close to 100%, up to energies of 40 keV for hybrid pixel detectors

Synthesis, characterization, crystal structure and DFT study of two new polymorphs of a Schiff base (E)-2-((2,6-dichlorobenzylidene) amino)benzonitrile

International audienceTwo new polymorphs of Schiff base, (E)-2-((2,6-dichlorobenzylidene)amino)benzonitrile, were prepared from the condensation of 4-amino-benzonitrile and 2,6-dichlorobenzaldehyde. The two polymorphs crystallize in two different space groups: P21/c for polymorph (I) with volume 1264.23(2) angstrom(3) and Pbca for polymorph (II) with volume 2469.3(2) angstrom(3). The two polymorphs have been characterized by FT-IR and UV-VIS spectroscopy. The crystal structures of both compounds were determined by single X-ray analysis. The difference between the two polymorphs was observed at the angle between the two phenyl rings which is 4.81 degrees for the first one and 82.27 degrees for the second one. Both crystal structures are built on the basis of moderate and weak hydrogen bonds. Theoretical calculations on isolated molecules at the MP2 cc-pVDZ level show that the two polymorphs correspond to two molecular conformations that are within less than 1 kJ mol(-1) and DFT periodic calculations indicate that (II) is more stable than (I) by 4.1 kJ mol(-1) of formula unit. Additionally, we performed TD-DFT calculation for free ligands to support the experimental data

Molecular saddles, 3. Hydroxymethyl-functionalised 9,10- bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene pi-electron donors as synthetic intermediates for supramolecular structures

The synthesis of new derivatives of 9,10-bis(1,3-dithiol-2- ylidene)-9,10-dihydroanthracene is reported. H-1 NMR studies on compound 4 are consistent with two conformers of the saddle- shaped molecule which interconvert by a boat-boat flipping of the central ring at high temperature. The hydroxymethyl substituent of 4 is readily esterified to yield the benzoyl and 2-naphthaloyl ester derivatives 5a and 5b, respectively, and the dimer and the trimer structures 6 and 7, respectively, by reaction with benzoyl chloride, 2-naphthaloyl chloride, 1,4- benzenedicarbonyl chloride and 1,3,5-benzenetricarbonyl chloride. Deprotonation of 9-(4,5-dimethyl-1,3-dithiol-2- ylidene)-10-(1,3-dithiol-2-ylidene)-9, 10-dihydroanthracene (8) using lithium bis(trimethylsilyl) amide (LHMDS) followed by in situ quenching of the Lithiated intermediate with methylchloroformate gave the diester derivative 10 (96% yield), whereas using LDA gave the monoester 9 as the major product (32% yield). Diester 10 was reduced to the di(hydroxymethyl) derivative 11. The solution electrochemistry of these new compounds has been studied by cyclic voltammetry: the ester substituents of 9 and 10 are conjugated to the pi -framework, causing a positive shift of E-OX. The X-ray crystal structures of compounds 4, 5a, 5b . CH2Cl2, 10 and 11 are reported. The molecules adopt a saddle-like conformation; the bis(1,3- dithiol-2-ylidene)-9,10-dihydroanthracene system is U-shaped due to the boat conformation of the central quinodimethane ring and folding of both the 1,3-dithiole rings. Each compound displays a dimeric packing motif which is most pronounced for 5a and 5b . CH2Cl2. Both these structures contain "oligomeric" acceptor donor stacks: 4-layer ADDA in 5a and 6-layer DADDAD in 5b (D = dithiole; A = benzoyl and naphthoyl, respectively) but neither contains infinite stacks

A new copper(II) coordination polymer containing chains of interconnected paddle-wheel antiferromagnetic clusters

The construction of supra­molecular architectures based on inorganic–organic coordination frameworks with weak noncovalent inter­actions has implications for the rational design of functional materials. A new crystalline binuclear copper(II) one-dimensional polymeric chain, namely catena-poly[[[tetra­kis­(μ-4-aza­niumyl­butano­ato-κ2O:O′)dicopper(II)(Cu—Cu)]-μ-chlorido-[di­aqua­dichlo­rido­copper(II)]-μ-chlorido] bis­(perchlorate)], {[Cu3Cl4(C4H9NO2)4(H2O)2](ClO4)2}n, was obtained by the reaction of 4-amino­butyric acid (GABA) with CuCl2·2H2O in aqueous solution. The structure was established by single-crystal X-ray diffraction and was also characterized by IR spectroscopy and magnetic measurements. The crystal structure consists of [{Cu2(GABA)4}{CuCl4(H2O)2}]+ cations and isolated perchlorate anions. Two symmetry-related CuII centres are bridged via carboxyl­ate O atoms into a classical paddle-wheel configuration, with a Cu...Cu distance of 2.643 (1) Å, while bridging Cl atoms complete the square-pyramidal geometry of the metal atoms. The Cl atoms connect the paddlewheel moieties to a second CuII atom lying on an octa­hedral site, resulting in infinite helical chains along the c axis. The packing motif exhibits channels containing free perchlorate anions. The crystal structure is stabilized by hydrogen bonds between the perchlorate anions, the coordinated water mol­ecules and the ammonium groups of the polymeric chains. The magnetic analysis of the title compound indicates a nontrivial anti­ferromagnetic behaviour arising from alternating weak–strong anti­ferromagnetic coupling between neighbouring CuII centres