Tetrabenzylcyclen as a receptor for fluoride

A tetraazacyclic ligand, tetrabenzylcyclen (L), was synthesized using an improved method with a higher yield by treatment of cyclen with benzylchloride in the presence of potassium carbonate. The reaction of L with an aqueous solution of fluorosilicic acid yielded a mixed-anionic salt with the composition [H3L][F][SiF6]$4H2O (1). The single crystal X-ray study revealed that the macrocyclic trication essentially changes the conformation compared to the free ligand in order to tightly accommodate the fluoride inside and to keep the hexafluorosilicate anions and water molecules outside in the solid state complex

Preparation, structure and properties of pyridinium/bipyridinium hexafluorosilicates

Pyridinium hexafluorosilicates with the compositions (LH)2[SiF6] (where L = 2,6-bis(hydroxymethyl)-pyridine (I), 4,5-bis(hydroxymethyl)-2-methylpyridine-3-ol (II)), monohydrate (LH)2[SiF6]H2O (L = 2-bromo-6-methylpyridine (III)) and (LH2)[SiF6] (L = 4,40-bipyridine (IV), 2,20-bipyridine (V)) were separated as crystalline products of interaction of fluorosilicic acid with different pyridines. All compounds were characterized by elemental analysis, IR, NMR 19F and mass-spectrometry, solubility data, and X-ray crystallography. The structural study revealed the details of the anion binding and solid state supramolecular architectures provided by the combination of the plethora of intermolecular interactions including strong charge assisted and conventional hydrogen bonds of NH F, OH F types along with O Br contacts and p–p interactions. The relationship between the salts structure and physico-chemical properties is discussed

Unexpected molecular flip in solid-state photodimerization.

Three cocrystals of the light-stable compound 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol (I) with light-sensitive molecules 1,2-dimethyl-2(1H)-pyridinone (a), 6-methyl-2(1H)-pyridinone (b), and 2-methyl-2(1H)-pyridinone (c) were exposed to UV light. The light-sensitive molecules undergo molecular flip. The estimated activation energy of the flip is 9.72 kJ/mol. The kinetics of the reaction of I-c was studied showing sigmoidal behavior with Avrami exponent of n = 0.95(6), suggesting homogeneous reaction

A structural investigation of the coordination behaviour of 4,6-dimethylpyrimidine-2-thiol with Zinc (II) at pH 6-A zwitterionic complex exhibiting unusual ZnS3N2 chromophore in solid state

Complexation between Zn2+ and 4,6-dimethylpyrimidine-2-thiol was attempted with ZnO, ZnSO4 and Zn(OAc)(2) In all cases, the same compound, tris-4,6-dimethylpyrimidine-2-thiolato zinc (II) was generated without anion incorporation It crystallized from methanol in the space group P2(1)/a. Z = 4 The molecular structure exemplifies an uncommon coordination of 3 ligands to Zn(II) through their thiolate centres: one of the ligands is protonated to effectively form a zwitterionic complex, which exhibits capped rectangular pyramidal coordination geometry of an anionic ZnN2S3 chromophore. In crystalline state. the ligand moieties differ in respect of orientations and interactions while in solution they behave as identical components of a symmetric molecule The crystal structure is stabilized by pi stacking and periodic H-bonding interactions along a. The presence of a protonated azomethine N in one ol the ligands is confirmed from the high conductance and acidic pH of an aqueous methanolic solution of the complex (C) 2009 Elsevier B V All rights reserve

Molecular mechanics-assisted crystal engineering of solid state photoreactions: application to the Yang photocyclization of a-1-norbornylacetophenone derivatives.

Based on mol. mechanics, Yang photocyclization of a-1-norbornylacetophenone derivs. in the cryst. state was engineered through methylation adjacent to the carbonyl group, thus changing the conformation in the crystal and leading to enhanced diastereo- and enantioselectivity

Hexafluorosilicates of bis(carboxypyridinium) and bis(2-carboxyquinolinium)

The preparation and characterization of three isomeric carboxypyridinium and carboxyquinolinium hexafluorosilicate salts is described. The salts of the general formulas (LH)2[SiF6] (I–III, L = 2-carboxypyridine, 3-carboxypyridine, 4-carboxypyridine) and (LH)2[SiF6]2H2O (IV, L = 2-carboxyquinoline) were prepared from the protonation reaction of the corresponding pyridine carbonic acid by the fluorosilicic acid. The compounds were characterized by IR, mass-spectrometry, thermogravimetric analysis, solubility data, and in the case of III by X-ray crystallography. The relationship between the salts solubility and the H-bonding system was analysed