7 research outputs found
A New Ring Bromination Method for Aromatic Compounds under Solvent-Free Conditions with Nbs/Al 2
No full textIntramolecular michael-type addition in the solid state
No full textSeveral 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
C-H···N mediated hexagonal network in the crystal structure of the 1:1 molecular complex 1,3,5-tricyanobenzene-hexamethylbenzene
No full textMolecules 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
Molecular recognition via lodo ... nitro and lodo ... cyano interactions: crystal structures of the 1 : 1 complexes of 1,4-diiodobenzene with 1,4-dinitrobenzene and 7,7,8,8-tetracyanoquinodimethane (TCNQ)
No full textMutual recognition of iodo and nitro groups through symmetrical iodo-nitro bridging interactions generates symmetrical molecular ribbons in the crystal structure of the 1 : 1 complex of 1,4-diiodobenzene 1 with 1,4-dinitrobenzene 2; however, in the crystal structure of the 1 : 1 complex of 1 with TCNQ, the mediation of simple, non-bridging -I ... N≡C interactions leads to the formation of skewed ribbons
Supramolecular synthons in crystal engineering. Structure simplification, synthon robustness and supramolecular retrosynthesis
No full textThe analogy between crystal engineering and traditional organic synthesis is outlined with reference to a family of crystal structures which incorporate iodo…nitro and carboxyl dimmer supramolecular synthons
The nature of halogen···halogen interactions and the crystal structure of 1,3,5,7-tetraiodoadamantane
No full textAn analysis of halogen halogen (X X) intermolecular interactions in crystals, using the Cambridge Structural Database (CSD). is presented. A total of 794 crystal structures yielded 1051 contacts corresponding to symmetrical and unsymmetrical X X interactions of the type Cl ···Cl, Br ···Br, I··· I, Cl ···F, Br ···F, I ···F, Br··· Cl, I ···Cl and I ···Br. These 1051 contacts are divided mainly into two categories, type I and type II depending upon the values of the two C-X··· X angles θ <SUB>1</SUB>and θ <SUB>2</SUB>around the X atoms in a fragment of the type C-X ···X-C. Type I contacts are defined as those in which θ <SUB>1</SUB>=θ <SUB>2</SUB> while type II are defined as those in which θ <SUB>1</SUB> ≅ 90° and θ <SUB>2</SUB> ≅ 180<SUP>°</SUP> . Our results indicate that as the polarisability of the X atom increases, type II contacts become more significant than type I contacts and the X ···X interaction may be more nearly considered to arise from specific attractive forces between the X atoms. A number of these concepts are succinctly illustrated in the crystal structure of 1,3,5,7-tetraiodoadamantane, 1. This structure has been reported to a very limited accuracy previously and the present work reveals an unusual twinned structure for this compound wherein the geometry of the stabilising I ···I interactions is retained across the twin boundary. Compound 1 is tetragonal, space group I41/a, a= b = 7.1984(7) and c= 28.582(4)Å, and Z = 4. The packing of the molecules in the crystal is controlled by I··· I interactions. The supramolecular network of I··· I connected molecules in crystalline 1 is closely related to that in adamantane-1,3,5,7-tetracarboxylic acid. Indeed, the stabilising nature of the I I interactions is crucial for the crystallisation of 1 in this particular structure because otherwise, it should also have formed plastic crystals as do the analogous tetrachloro and tetrabromo derivatives.An analysis of halogen halogen (X X) intermolecular interactions in crystals, using the Cambridge Structural Database (CSD). is presented. A total of 794 crystal structures yielded 1051 contacts corresponding to symmetrical and unsymmetrical X X interactions of the type Cl ···Cl, Br ···Br, I··· I, Cl ···F, Br ···F, I ···F, Br··· Cl, I ···Cl and I ···Br. These 1051 contacts are divided mainly into two categories, type I and type II depending upon the values of the two C-X··· X angles θ and θ around the X atoms in a fragment of the type C-X ···X-C. Type I contacts are defined as those in which θ =θ while type II are defined as those in which θ ≅ 90° and θ ≅ 180 . Our results indicate that as the polarisability of the X atom increases, type II contacts become more significant than type I contacts and the X ···X interaction may be more nearly considered to arise from specific attractive forces between the X atoms. A number of these concepts are succinctly illustrated in the crystal structure of 1,3,5,7-tetraiodoadamantane, 1. This structure has been reported to a very limited accuracy previously and the present work reveals an unusual twinned structure for this compound wherein the geometry of the stabilising I ···I interactions is retained across the twin boundary. Compound 1 is tetragonal, space group I41/a, a= b = 7.1984(7) and c= 28.582(4)Å, and Z = 4. The packing of the molecules in the crystal is controlled by I··· I interactions. The supramolecular network of I··· I connected molecules in crystalline 1 is closely related to that in adamantane-1,3,5,7-tetracarboxylic acid. Indeed, the stabilising nature of the I I interactions is crucial for the crystallisation of 1 in this particular structure because otherwise, it should also have formed plastic crystals as do the analogous tetrachloro and tetrabromo derivatives
