Kaliyamoorthy Panneerselvam

Molecular recognition involving an interplay of O–H⋯O, C–H⋯O and π⋯π interactions. The anomalous crystal structure of the 1 : 1 complex 3,5-dinitrobenzoic acid–4-(N,N-dimethylamino)benzoic acid

The crystal structure of the 1:1 donor–acceptor complex of 3,5-dinitrobenzoic acid and 4-(N,N-dimethylamino)benzoic acid contains the uncommon O–H ⋯ O hydrogen-bonded carboxy homodimers rather than the heterodimers found in nine other related complexes. The formation of these homodimers contradicts the general principle that in hydrogen-bonded networks, the strongest proton donor hydrogen bonds to the strongest proton acceptor. This unusual homodimer is obtained because of difficulties in C–H ⋯ O hydrogen bond formation, the consequent importance of π⋯π stacking interactions and the enhanced stability of homodimer stacks over heterodimer stacks. Additionally, it is concluded that: (i) O–H ⋯ O hydrogen bonds can act as a conduit for charge transfer and may alter the polarization of atoms; (ii) C–H ⋯ O bonds can be used for molecular recognition and C–H ⋯ O patterns are sensitive to molecular stoichiometry and substituent positioning; (iii) stacking interactions influence the nature of hydrogen bonding and vice versa. This study shows that for precise supramolecular construction, strong and weak intermolecular interactions must be considered together.

C–H ⋯ N mediated hexagonal network in the crystal structure of the 1 : 1 molecular complex 1,3,5-tricyanobenzene–hexamethylbenzene

Molecules of 1,3,5-tricyanobenzene are networked with C–H ⋯ N hydrogen bonds into a symmetrical hexagonal pattern in the crystal structure of the 1 : 1 complex formed by the compound with hexamethylbenzene.

Crystal structure of the 2:1 complex of mercury(II) chloride with trithiapyridino-12-crown-4 having unusual mercury coordination

The single crystal X-ray analysis of the 1:2 complex between trithiapyridino-12-crown-4 ( 1 ) and HgCl 2 is reported. Crystals of the complex are monoclinic, P 2 1 / n , with a =13.455(5), b =15.627(2), c =8.933(2) A, β=93.42(2)° and D c =2.844 g cm −3 for Z =4. The host macrocycle has an approximate non-crystallographic mirror symmetry. The structure contains Hg in two very different environments. One Hg is fivefold coordinated in distorted square pyramidal geometry using the four heteroatoms of the macroring and an additional chloro atom as ligating sites. The other Hg remains uncoordinated by the macroring but is surrounded by three chloro atoms to form a trigonal-planar geometry. This complex is an example of unique coordination mode around Hg.

Hexagonal supramolecular networks in the crystal structure of the 1:1 molecular complex trimethylisocyanurate–1,3,5-trinitrobenzene

Trimethylisocyanurate 2 and 1,3,5-trinitrobenzene 3 form a hexagonal C–H ⋯ O mediated 1:1 complex wherein distinct molecular layers are formed, the molecular symmetry of the components being retained in the crystal.

Macro-rings designed for uncharged molecule complexation. Synthesis, complex formation, and structural studies of new pyridino crowns incorporating resorcinol and hydroquinone building blocks. X-Ray crystal and molecular structure of a 22-membered pyridino crown

The crystal structure of the pyridino crown (2) containing a resorcinol group is reported. Two crystallographically independent molecules of compound (2) with considerably different conformations are present in the crystal. Both molecules provide a potential cavity, but have other steric factors highly unfavourable for complex formation. Also, there is no free space in the crystal lattice for accommodation of a guest molecule. Based on this result, three pyridino crowns of different ring size incorporating two resorcinol units in different positions (5a–c) have been synthesized, together with the hydroquinone-group-containing analogues (6a–c). The host properties of the new macro-rings were determined. It was found that compound (6c) forms crystalline inclusion complexes with a number of dipolar aprotic and rather apolar organic guests such as nitromethane, acetonitrile, DMF, or dioxane, while the other compounds are inefficient. Host–guest relationships are discussed and conclusions for future host design are drawn.

The structure of the uncharged-molecule complex between a dinaphthopyridino-18-crown-6 host and acetonitrile (1 : 2)

Single crystal X-ray analysis of a 1 : 2 complex between the dinaphthopyridino-l8-crown-6 host (1) and acetonitrile is reported. Crystals of the complex are monoclinic,P21/c witha = 12.178(5),b = 8.186(1),c = 30.873(1) Å, β = 96.86(1)°, andDc = 1.25 g cm−3 forZ = 4. The host molecule reveals an approximate mirror symmetry and exists in a so-called ‘dentists chair’ conformation. One of the acetonitrile guest molecules is involved in possible weak interactions to two oxygen atoms of the host macroring, while the other fills free lattice space only.

Zn(II) and Hg(II) complexes of 4,6-diamino-2-thiopyrimidine and 4,6-diamino-2-methylthiopyrimidine. Crystal structure of 4,6-diamino-2-methylthiopyrimidinium hemitetrachlorozincate(II)

Abstract Reaction of Zn(II) and Hg(II) with 4,6-diamino-2- thiopyrimidine (DATP) and 4,6-diamino-2-methylthiopyrimidine (DAMTP) in aqueous medium gave six new compounds which have been characterized by elemental analysis, IR and 1H NMR spectroscopic techniques. The crystal structure of the Zn(II) complex of DAMTP has been determined by X-ray diffraction. It crystallizes in the trigonal space group P3121 (or P3221), a=8.725(2), c=24.288(4) A, C5H9Cl2N4SZn0.5, Z=6, Dcalc=1.616 g cm−3 and R=0.045 for 1056 unique reflections. The compound forms a salt structure composed of a 4,6- diamino-2-methylthiopyrimidinium cation with the ring nitrogen N1 protonated and a hemitetrachlorozincate anion. The crystal packing is dominated by a three-dimensional network of NH…Cl hydrogen bonds.

Intramolecular Michael-type addition in the solid state

Several substituted 2′-hydroxy-4′,6′-dimethylchalcones undergo a solid state Intramolecular Michaeltype addition reaction to yield the corresponding flavanones, at temperatures significantly below the melting points of the reactants or products. Single crystal X-ray diffraction studies of the reactant and product phases have been carried out and indicate that these solid state reactions most likely proceed in a non-topochemical fashion. A similar conclusion is deduced from X-ray powder diffraction, differential scanning calorimetry and packing energy calculations. Reaction in the defect regions is probably important because considerable relaxation in the molecular conformation of the chalcone is required in the crystal before Intramolecular ring-closure to the flavanone can occur.

Solid state structure of the hydrated potassium thiocyanate complex of benzodinaphthopyridino-21-crown-7, C37H31NO6.KSCN.H2O (1:1:1)

Single crystal X-ray analysis of the hydrated KSCN complex of benzodinaphthopyridino-21-crown-7 (1) (1 : 1 : 1) is reported. Crystals of the complex are orthorhombic,Pnma, withα = 16.946(4),b = 22.298(4),c = 10.390(8) Å andDc = 1.184 g cm−1,Z = 4. The host macroring (1) has a mirror symmetry and exists in a so-called ‘dentists chair’ conformation. The cation (K−) is coordinated to all the six ether oxygen atoms and also weakly to the pyridine N atom. The SCN− anion group has a statistical type of disorder with opposite orientations of S and N such that nitrogen and sulphur are coordinated to K+. Packing of the host molecules is in columns to form quasi channels with K+, SCN−, and H2O being located inside the stacks.