Cl-35 NQR study of lattice dynamic and magnetic property of a crystalline coordination polymer {CuCA(phz)(H2O)2}n

Copper(II) compounds {CuCA(phz)(H2O)2}n (H2CA = chloranilic acid, phz = phenazine) having a layer structure of -CuCA(H2O)2- polymer chains and phenazine was studied by 35Cl nuclear quadrupole resonance (NQR). The single NQR line observed at 35.635 MHz at 261.5 K increased to 35.918 MHz at 4.2 K. The degree of reduction of electric field gradient due to lattice vibrations was similar to that of chloranilic acid crystal. Temperature dependence of spin-lattice relaxation time, T1, of the 35Cl NQR signal below 20 K, between 20 and 210 K, and above 210 K, was explained by 1) a decrease of effective electron-spin density caused by antiferromagnetic interaction, 2) a magnetic interaction between Cl nuclear-spin and electron-spins on paramagnetic Cu(II) ions, and 3) an increasing contribution from reorientation of ligand molecules, respectively. The electron spin-exchange parameter |J| between the neighboring Cu(II) electrons was estimated to be 0.33 cm−1 from the T1 value of the range 20−210 K. Comparing this value with that of J = −1.84 cm−1 estimated from the magnetic susceptibility, it is suggested that the magnetic dipolar 2 coupling with the electron spins on Cu(II) ions must be the principal mechanism for the 35Cl NQR spin-lattice relaxation of {CuCA(phz)(H2O)2}n but a delocalization of electron spin over the chloranilate ligand have to be taken into account.</p

Crystal structure of 4-chloro-2-nitrobenzoic acid with 4-hydroxyquinoline: a disordered structure over two states of 4-chloro-2-nitrobenzoic acid-quinolin-4(1H)-one (1/1) and 4-hydroxyquinolinium 4-chloro-2-nitrobenzoate

The title compound, C9H7.5NO center dot C7H3.5ClNO4, was analysed as a disordered structure over two states, viz. co-crystal and salt, accompanied by a keto-enol tautomerization in the base molecule. The co-crystal is 4-chloro-2-nitrobenzoic acid-quinolin-4(1H)-one (1/1), C7H4ClNO4 center dot C9H7NO, and the salt is 4-hydroxy-quinolinium 4-chloro-2-nitrobenzoate, C9H8NO+center dot C7H3ClNO4. In the compound, the acid and base molecules are held together by a short hydrogen bond [O center dot center dot center dot O = 2.4393 (15) angstrom], in which the H atom is disordered over two positions with equal occupancies. In the crystal, the hydrogen-bonded acid-base units are linked by N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds, forming a tape structure along the a-axis direction. The tapes are stacked into a layer parallel to the ab plane via pi-pi interactions [centroid-centroid distances = 3.5504 (8)-3.9010 (11) angstrom]. The layers are further linked by another C-H center dot center dot center dot O hydrogen bond, forming a three-dimensional network. Hirshfeld surfaces for the title compound mapped over shape-index and d orm were generated to visualize the intermolecular interactions

2-Chloro-4-nitro­benzoic acid–quinoline (1/1)

In the title compound, C7H4ClNO4·C9H7N, the two components are connected by an O—H⋯N hydrogen bond. In the hydrogen-bonded unit, the dihedral angle between the quinoline ring system and the benzene ring of benzoic acid is 3.15 (7)°. In the crystal, units are linked by inter­molecular C—H⋯O hydrogen bonds, forming a tape along the c axis. The tapes are stacked along the b axis through a C—H⋯O hydrogen bond into a layer parallel to the bc plane

Pyridine-3-carbonitrile–chloranilic acid–acetonitrile (2/1/2)

In the crystal structure of the title compound, 2C6H4N2·C6H2Cl2O4·2C2H3N, the two symmetry-related pyridine-3-carbonitrile mol­ecules are linked to either side of a chloranilic acid (systematic name: 2,5-dichloro-3,6-dihydr­oxy-1,4-benzoquinone) mol­ecule via inter­molecular O—H⋯N hydrogen bonds, giving a centrosymmetric 2:1 unit. The dihedral angle between the pyridine ring and the chloranilic acid plane is 26.71 (6)°. In addition, the two acetonitrile mol­ecules are linked to either side of the 2:1 unit through C—H⋯N hydrogen bonds, forming a 2:1:2 aggregate. These 2:1:2 aggregates are further linked by weak inter­molecular C—H⋯N and C—H⋯O hydrogen bonds, forming a tape along the c axis

Crystal structures of four isomeric hydrogen-bonded co-crystals of 6-methyl­quinoline with 2-chloro-4-nitro­benzoic acid, 2-chloro-5-nitro­benzoic acid, 3-chloro-2-nitro­benzoic acid and 4-chloro-2-nitro­benzoic acid

The structures of the four isomeric compounds of 6-methyl­quinoline with chloro- and nitro-substituted benzoic acids, C7H4ClNO4·C10H9N, namely, 2-chloro-4-nitro­benzoic acid–6-methyl­quinoline (1/1), (I), 2-chloro-5-nitro­benzoic acid–6-methyl­quinoline (1/1), (II), 3-chloro-2-nitro­benzoic acid–6-methyl­quinoline (1/1), (III), and 4-chloro-2-nitro­benzoic acid–6-methyl­quinoline (1/1), (IV), have been determined at 185–190 K. In each compound, the acid and base mol­ecules are linked by a short hydrogen bond between a carboxyl O atom and an N atom of the base. The O⋯N distances are 2.5452 (12), 2.6569 (13), 2.5640 (17) and 2.514 (2) Å, respectively, for compounds (I)–(IV). In the hydrogen-bonded acid–base units of (I), (III) and (IV), the H atoms are each disordered over two positions with O site:N site occupancies of 0.65 (3):0.35 (3), 0.59 (4):0.41 (4) and 0.48 (5):0.52 (5), respectively, for (I), (III) and (IV). The H atom in the hydrogen-bonded unit of (II) is located at the O-atom site. In all of the crystals of (I)–(IV), π–π inter­actions between the quinoline ring system and the benzene ring of the acid mol­ecule are observed. In addition, a π–π inter­action between the benzene rings of adjacent acid mol­ecules and a C—H⋯O hydrogen bond are observed in the crystal of (I), and C—H⋯O hydrogen bonds and O⋯Cl contacts occur in the crystals of (III) and (IV). These inter­molecular inter­actions connect the acid and base mol­ecules, forming a layer structure parallel to the bc plane in (I), a column along the a-axis direction in (II), a layer parallel to the ab plane in (III) and a three-dimensional network in (IV). Hirshfeld surfaces for the title compounds mapped over dnorm and shape index were generated to visualize the weak inter­molecular inter­actions

3-Hydroxy­pyridinium hydrogen chloranilate monohydrate

In the title salt hydrate, C5H6NO+·C6HCl2O4 −·H2O, the three components are held together by O—H⋯O and N—H⋯O hydrogen bonds, as well as by C—H⋯O contacts, forming a double-tape structure along the c axis. Within each tape, the pyridinium ring and the chloranilate ring are almost coplanar, forming a dihedral angle of 2.35 (7)°

4-Chloro-2-nitro­benzoic acid–pyrazine (2/1)

In the title co-crystal, 2C7H4ClNO4·C4H4N2, the pyrazine mol­ecule is located on an inversion centre, so that the asymmetric unit consists of one mol­ecule of 4-chloro-2-nitro­benzoic acid and a half-mol­ecule of pyrazine. The components are connected by O—H⋯N and C—H⋯O hydrogen bonds, forming a 2:1 unit. In the hydrogen-bonded unit, the dihedral angle between the pyrazine ring and the benzene ring of the benzoic acid is 16.55 (4)°. The units are linked by inter­molecular C—H⋯O hydrogen bonds, forming a sheet structure parallel to (04). A C—H⋯O hydrogen-bond linkage is also observed between these sheets

Hydrogen bonding in two solid phases of phenazine-chloranilic acid (1/1) determined at 170 and 93 K

The crystal structures in two solid phases, i.e. phase II stable between 146 and 253 K and phase IV below 136 K, of the title compound [phenazine-chloranilic acid (1/1), C12H8N2 center dot C6H2Cl2O4, in phase II, and phenazinium hydrogen chloranilate, C12H9N2+center dot C6HCl2O4-, in phase IV], have been determined. Both phases crystallize in P2(1), and each structure was refined as an inversion twin. In phase II, the phenazine and chloranilic acid molecules are arranged alternately through two kinds of O-H center dot center dot center dot N hydrogen bonds. In phase IV, salt formation occurs by donation of one H atom from the chloranilic acid molecule to the phenazine molecule; the resulting monocation and monoanion are linked by N-H center dot center dot center dot O and O-H center dot center dot center dot N hydrogen bonds

Morpholinium hydrogen chloranilate methanol monosolvate

In the crystal structure of the title compound, C4H10NO+·C6HCl2O4 −·CH4O, the components are held together by bifurcated O—H⋯(O,O), O—H⋯(O,Cl) and N—H⋯(O,O) hydrogen bonds into a centrosymmetric 2+2+2 aggregate. The aggregates are further connected by another bifurcated N—H⋯(O, O) hydrogen bond, forming a double-tape structure along the b axis. A weak C—H⋯O inter­action is observed between the tapes