M. Śledź

Crystal structure, phase transitions and vibrational spectra of bis(betaine) nitrate

Abstract The crystal structure of bis(betaine) nitrate (BBN) has been determined by X-ray diffraction as monoclinic, space group P2 1 / c , with a = 5.668(1), b = 11.259(2) and c = 23.073(5) A, β = 93.65(3)°, Z = 4. The crystal comprises nitrate ions, NO 3 − , and betaine dimers: two betaine moieties are joined by a very strong asymmetric hydrogen bond with an O···O distance of 2.449(2) A. Fist order type phase transitions at 394 K, 439 K and 460 K (melting and decomposition) and very likely second order type at about 448 K were discovered for the BBN sample by the Differential Scanning Calorimetry method. In the deuterated analogue they appear at 394 K, 434 K, 448 K and 459 K. The FTIR and FT-Raman spectra for the powder samples were measured at room temperature. Additionally the FTIR spectra were taken at low temperatures (till 10 K). A strong band at about 900 cm −1 arises from the ν a OHO vibration of the very strong hydrogen bond. The site symmetry of the NO 3 − anions is C 1 according to X-ray data and the vibrational spectra.

Synthesis, structural investigations and magnetic properties of dipyridinated manganese phthalocyanine, MnPc(py)2

Abstract The MnPc(py)2 complex was obtained in the reaction of MnPc with purified and dry pyridine under non-oxidation conditions. It crystallises in the centrosymmetric space group P21/c of the monoclinic system with two molecules per unit cell. The Mn2+ cation is coordinated by four N-isoindole atoms of phthalocyaninato(2−) macrocycle and axially by two nitrogen atoms of pyridine molecules into a tetragonal bipyramid. The MnPc(py)2 crystals are moderately stable under air, but in pyridine solution the MnPc(py)2 complex undergoes oxidation by O2 yieldings the binuclear manganese(III) μ-oxo complex (MnPcpy)2O as evidenced by the UV–Vis spectroscopy. The magnetic susceptibility measurement performed on solid sample of MnPc(py)2 shows the Curie–Weiss behaviour in the temperature region of 300–15 K. The calculated magnetic moment μeff indicates three unpaired electrons (S=3/2), thus the ground state configuration of Mn ion is (a1g)2(eg)2(b2g)1, and the MnPc(py)2 complex is the intermediate spin complex. Below 5.5 K (TN) the magnetic susceptibility sharply decreases due to the cooperative intermolecular antiferromagnetic interactions.

New crystalline modification of terephthalic acid

Abstract The new crystalline modification of terephthalic acid can be obtained either from the commercially available triclinic modification by heating at 250°C or directly by a thermal hydrolysis of p -dicyanobenzene. It crystallises in a monoclinic system, space group C 2/ m with a =8.940(2), b =10.442(2), c=3.790(1) A , V=353.7(2) A 3 , β =91.21(3)° and Z =2. Both carboxyl groups of terephthalic acid are coplanar with the phenyl ring. The molecules in the crystal are linked through the hydrogen bonds in the carboxyl groups into infinite chains. The orientational disorder is observed in the carboxyl groups. The structure of the monoclinic form is compared with the structure of both the triclinic modifications.

Crystal structure and vibrational spectra of betaine hydrogen selenate monohydrate

Abstract The crystal structure of betaine hydrogen selenate monohydrate, (C5H12NO2)+·(HSeO4)−·(H2O), BHSeH2O, has been determined by X-ray diffraction as monoclinic, space group P2 1 c with a = 6.674(6), b = 11.912(9), c = 14.156(14) A, β = 100.61(4)° and Z = 4. It comprises protonated betaine moieties (betainium cations), hydrogen selenate anions and water molecules which are held together by a number of hydrogen bonds and form infinite chains. Two types of four-membered centrosymmetric rings are distinguished in the chain. The two rings share a common side. Powder FT-IR and FT-Raman spectra were measured for the title crystal, the dehydrated crystal (betaine hydrogen selenate, BHSe) and their deuterated analogues. Assignments of the observed bands to vibrations of the hydrogen bonds and internal vibrations of the hydrogen selenate anions and the betainium cations are proposed. DSC data are also presented.

Crystal structures of 2- and 3-cyanopyridine

Abstract The crystals of 2- and 3-cyanopyridine isomers have been obtained by a sublimation method. The crystal structures of both isomers have been determined on the basis of low-temperature X-ray single crystal experiments and compared, also in relation to 4-cyanopyridine. In 2-cyanopyridine the nitrogen atom of the CN group, whereas in 3- the N-ring atom, is involved in the shortest intermolecular contact. In both cases, the hydrogen bond type interactions are rather of a weak nature, but they are important for developing of the polymeric chains.