Self-Assembly of Hydrogensquarates: Crystal Structures and Properties

Preparation and spectral properties of europium hydrogen squarate microcrystals

A simple scheme for preparation of europium hydrogen squarate octahydrate microcrystals, Eu(HSq)₃·8H₂O is demonstrated. The microcrystalline powders obtained have a potential application as non-centrosymmetric and UV radiation - protective hybrid optical material. The site-symmetry of the Eu - ion is C_2V or lower, obtained from diffuse reflectance spectra. The formation of europium hydrogen squarate is supported by IR - spectroscopy, UV-vis spectroscopy, chemical analysis and X-ray diffraction. A detailed analysis of the UV-vis and IR spectra of the micropowders prepared is presented.

3-Phenylpyridinium hydrogen squarate: experimental and computational study of a nonlinear optical material

The detailed investigation of an organic nonlinear optical (NLO) squarate salt of 3-phenylpyridinium hydrogen squarate (1), C11H10N+·C4HO4(-), was reported in this study. The XRD data indicates that the crystal structure of the title compound is in the triclinic P-1 space group. In the asymmetric unit, the 3-phenylpyridine molecule is protonated by one hydrogen atom donation of squaric acid molecule, forming the salt (1). The X-ray analysis shows that the crystal packing has hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through NH···O interactions. The structural and vibrational properties of the compound were also studied by computational methods of ab initio at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) levels of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 are presented and compared with the experimental results. Non-linear optical properties (NLO) of the title compound together with the molecular electrostatic potential (MEP), electronic absorption spectrum, frontier molecular orbitals (FMOs) and conformational flexibility were also studied at the 2 level and the results were reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

2-Pyridinium propanol hydrogen squarate: experimental and computational study of a nonlinear optical material

The experimental and theoretical investigation of a novel organic nonlinear optical (NLO) squarate salt of 2-pyridinium propanol hydrogen squarate (1), C8H12ON(+)·C4HO4(-), were reported in this study. The crystal structure of the title compound was found to crystallize in the triclinic P-1 space group. In the asymmetric unit each squaric acid molecules have donated one H atom to the pyridines N1 and N2 atoms of a 2-pyridine propanol molecule, forming the salt (1). The X-ray analysis clearly indicated that the crystal packing has shown the hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through N-H⋯O interactions. The structural and vibrational properties of the compound were also studied by computational methods of ab initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 are presented and compared with the X-ray analysis result. The molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

Synthesis, an experimental and quantum chemical computational study: proton sharing in 4-Morpholinium bis(hydrogen squarate)

The experimental and theoretical investigation results of a novel organic squarate salt of 4-Morpholinium bis(hydrogen squarate) (1), C₆H₁₄ON(+)·C₈H₃O₈(-), were reported in this study. The crystal structure of the title compound was found to crystallize in the triclinic P-1 space group. In the crystals of 1 the morpholine ring adopts the chair conformation with the ethyl group in the equatorial and hydrogen atoms in axial positions. The hydrogen squarate anions are linked into a homoconjugated anion, [(HSQ)₂H], by a short symmetric, nonlinear O₈⋯H₂⋯O₂ hydrogen bond of 2.444 (2)Å. The structural and vibrational properties of the compound were also studied by computational methods of ab-initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The obtained calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 obtained are presented and compared with the X-ray analysis result. On the other hand the molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

Synthesis, an experimental and quantum chemical computational study of a new nonlinear optical material: 2-picolinium hydrogensquarate

The experimental and theoretical investigation results of a novel organic non-linear optical (NLO) organic squarate salt of 2-Picolinium hydrogensquarate (1), C6H8N+·C4HO4-, were reported in this study. The space group of the title compound was found in the monoclinic C2/c space group. It was found that the asymmetric unit consists of one monohydrogen squarate anion together with mono protonated 2-Picolinium, forming the (1) salt. The X-ray analysis clearly indicated that the crystal packing has shown the hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through NH⋯O interactions. The hydrogensquarate anions form α-dimer, while 2-Picolinium molecule interacts through NH⋯O and CH⋯O with the hydrogensquarate anion. The structural and vibrational properties of the compound were also studied by computational methods of ab initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 obtained are presented and compared with the X-ray analysis result. On the other the molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

NH⋯O and OH⋯O interactions of glycine derivatives with squaric acid

Hydrogen-bonded complexes of glycine, sarcosine, dimethylgycine and betaine with squaric acid have been synthesized and characterized by X-ray diffraction, FTIR, NMR and DFT methods.

Biguanide and squaric acid as pH-dependent building blocks in crystal engineering

Biguanides and squaric acid are attractive partners for crystal engineering: they incorporate multiple sites that can donate or accept hydrogen bonds. Protonation equilibria in their solutions and the outcome of crystallization experiments are pH dependent: 10 different salts have been obtained from N,N-dimethylbiguanide, N-phenylbiguanide and N-o-tolylbiguanide.

Solid-state UV-MALDI-MS assay of transition metal dithiocarbamate fungicides

The determination of transition metal containing dithiocarbamate fungicides represents a challenging aspect of analytical object. They have a low stability, low solubility and stabilize versatile coordination monomers, dimers, disulfides and/or S-oxidized derivatives. Their diverse biological activities and agricultural implementation encompass plant prevention and crop protection against a variety of plants containing fungi and diseases of 400 pathogens and 70 cultures. Nonetheless, those dithiocarbamates (DTCs) are banned for agricultural use in Europe or have expiration at years 2016-2017 because of their highly toxic degradation products and/or metabolites, in particular ethylene thiourea; they found large-scale implementations in materials research and medicine. Despite the broad interdisciplinary of DTC application, due to the above reasons, they have received little attention in the rapidly growing field of analytical chemistry, and in particular, the analytical mass spectrometry. Therefore, the study reported on qualitative, quantitative and structural analysis of ten DTCs (1-10), using the matrix assisted laser desorption/ionization (UV-MALDI)-Orbitrap-mass spectrometry (MS) contributed considerably to the implementation of the method for environmental and foodstuffs monitoring. Its ultrahigh resolving power and capacity for direct solid-state analysis, at limited number of sample pretreatment steps, at concentration levels of analytes of up to femtogram per gram resulted to achievement of a highly precise analytical information for these non-trivial objects. The presented fully validated method and technique is based on the successful ionization of DTCs embedded in three novel organic salts (M1-M3). In this regard, the reported MS and the single-crystal X-ray diffraction data as well as the quantum chemical one are able to correlate the molecular structures in condense and in the gas phase. Despite the novelty of the fundamental methodological character of the research reported, the promising metrology contributed to the applied aspect of the UV-MALDI-MS as a robust analytical method for environmental and foodstuffs monitoring, which is tested on two commercially available crop protecting products such as Mancozeb® and Antracol®, respectively.

Vibrational spectral studies and non-linear optical properties of L-leucine L-leucinium picrate: a Density Functional Theory approach

Single crystals of l-leucine l-leucinium picrate were grown by slow evaporation at room temperature and were characterized by X-ray powder diffraction study to confirm the crystalline nature of the synthesized compound. The optimized molecular structure, vibrational spectra and the optical properties were calculated by the Density Functional Theory (DFT) method using the B3LYP function with the 6-31G(d) basis set. Good consistency is found between the calculated results and the experimental structure, IR, and Raman spectra. The detailed interpretation of the vibrational modes was carried out. The natural bond orbital (NBO) analysis, confirms the occurrence of intermolecular hydrogen bonds that are responsible for the stabilization of the title compound, leading to high nonlinear optical (NLO) activity. The lowering in the HOMO and LUMO energy gap explains the eventual charge transfer interactions that take place within the molecules.

Salts of aromatic amines: crystal structures, spectroscopic and non-linear optical properties

Crystal structures, spectroscopic and NLO properties of 8 novel organic salts with aromatic amines, i.e. tyrammonium iodide (1), tyrammonium benzene-1,2,4-tricarboxilate (2), octopammonium 5-sulfosalicylate monohydrate (3), octopammonium hydrogen squarate (4), dopammonium 5-sulfosalicylate dihydrate (5), ephedrinium mandelate (6), dopammonium hydrogen squarate (7) and bis(ephedrinium) squarate (8) are reported and discussed with a view of their application in optical technologies. The conformations of the cations of the aromatic amines are discussed comparing the experimental and theoretical data.

Synthesis, spectroscopic and structural study of trans- and cis-(±)-3-phenyl-4-(pyrrolidine-1-carbonyl)-isochroman-1-ones

Synthesis, spectroscopic and structural study of trans- and cis-(±)-3-phenyl-4-(pyrrolidine-1-carbonyl)-isochroman-1-ones is performed in order to obtain the correlation between the crystal structure and spectroscopic properties of both isomers in solid-state. The methods such as single crystal X-ray diffraction, conventional and linear-polarized IR-spectroscopy, UV-spectroscopy, mass spectrometry, ¹H and ¹³C NMR are employed. Quantum chemical ab initio and DFT calculations are performed, to support the experimental data for the electronic structure and optical properties.