• Volume 122, Issue 5

September 2010,   pages  665-785

• Foreword

• Crystal engineering: A brief overview

Crystal structures of organic and metal-organic compounds have been determined in enormous numbers over the past century, and at the time of writing this review, the Cambridge Structural Database has just crossed the half million mark. The possibility of designing a particular crystal packing is, however, of more recent origin and the subject of crystal engineering has addressed this possibility, more or less systematically, during the past 30 years. Crystal engineering demands a detailed and thorough knowledge of intermolecular interactions, which act as the supramolecular glue that binds molecules into crystals. It also requires systematic strategies for the design of a crystal, the architectural blueprint as it were. Finally, this enterprise needs to be geared towards a useful property in that the crystal that is being designed is a functional one. All these features of the subject are directly or indirectly connected with the fact that there is a very large database of known crystal structures that is available to the crystal engineer. This review attempts to briefly survey the current scenario in this expanding subject.

• Analysis of Cl…Cl and C-H…Cl intermolecular interactions involving chlorine in substituted 2-chloroquinoline derivatives

Six crystal structures of substituted 2-chloroquinoline derivatives have been analysed to evaluate the role of Cl atom as a self recognizing unit resulting in the formation of Cl…Cl and C-H…Cl interactions to generate supramolecular assembly in the solid state. The features of Type I and Type II geometries associated with Cl…Cl interactions have been analysed to show directional preferences leading to differences in the packing motifs in these crystal structures. C-H…Cl interactions are generated exclusively in structures depicting Type II Cl…Cl interaction have been observed in these structures.

• Synthesis and structure of diorganotin dibromides, R2SnBr2 (R = 2,4,6-trimethylphenyl or 2,4,6-trimethylbenzyl): Hydrolysis of (2,4,6-Me3C6H2)2SnBr2

The reaction of SnBr4 with in situ generated 2,4,6-trimethylphenylmagnesium bromide afforded a mixture of (2,4,6-Me3C6H2)2SnBr2 (1) and (2,4,6-Me3C6H2)3SnBr (2) which could be separated from each other by their solubility differences in diethyl ether. On the other hand, the reaction of tin metal with 2,4,6-Me3C6H2CH2Br afforded (2,4,6-Me3C6H2CH2)2SnBr2 (3). Hydrolysis of the latter using triethylamine as the base afforded [{(2,4,6-Me3C6H2CH2)2Sn}2(𝜇-O)(Br)(𝜇-OH)]2.2CH2Cl2 (4) while the use of NaOH as the base afforded [{(2,4,6-Me3C6H2CH2)2Sn}2(𝜇-O)(OH)(𝜇-OH)]2.2CH2Cl2 (5). Compounds 4 and 5 are dimeric tetraorganodistannoxanes consisting of a central distannoxane (Sn2O2) motif.

• A novel tetraarylpyrene host: Conformation-dependent inclusion of guest molecules in the crystal lattice

Tetrakis(2,6-dimethyl-4-acetoxyphenyl)pyrene H2 containing flexible acetate functionalities at the para positions of sterically-hindered and rigid aryl rings functions as an inclusion host system. Depending on the orientations of the acetate functionalities, a variety of conformers may indeed be expected. A limited number of the crystal structures of the inclusions compounds of H2 reveal that one indeed observes 2 different conformations for the host based on the orientations of the acetate functionalities. The inclusion compound of H2 with benzene guest molecules is particularly appealing in terms of how the latter are held in trough domains of the host by weak C−H$\cdots$O and C−H$\cdots \pi$ hydrogen bonds. More experimentation and analyses of crystal structures of such systems is expected to lead to better insights toward realizing multicomponent molecular crystals in a rational manner.

• Assembling one-dimensional coordination polymers into threedimensional architectures via hydrogen bonds

The reactions of bis(pyridylcarboxamido)alkanes (amides) and bis(3-pyridyl)alkanediamides (reverse amides) with copper(II) and zinc(II) in the presence of various anions resulted in onedimensional polymeric crystalline complexes with or without guest inclusion. The crystal structure analyses of these complexes reveal that the one-dimensional networks observed here are of three types: simple linear chain, chains with wavy nature and chains containing cavities. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via N-H$\cdots$O hydrogen bonds.

• Powder diffraction in structural characterization of dienediaminoketones of the indolin-3-one series

Crystal structures of five derivatives of dienediaminoketones - 3-amino-3-(dimethylamino)-2-[(3-oxo-1,3-dihydro-2H-indol-2-ylidene)methyl]acrylonitrile (1); 3-amino-2-[(3-oxo-1,3-dihydro-2Hindol-2-ylidene)methyl]-3-pyperidin-1-ylacrylonitrile (2); 3-amino-3-morpholin-4-yl-2-[(3-oxo-1,3-dihydro-2H-indol-2-ylidene)methyl]acrylonitrile (3); 3-amino-3-[(4-methoxyphenyl)amino]-2-[(3-oxo-1,3-dihydro-2H-indol-2-ylidene)methyl]acrylonitrile (4) and 3-amino-3-(benzylamino)-2-[(3-oxo-1,3-dihydro-2H-indol-2-ylidene)methyl]acrylonitrile (5) - were determined from powder patterns measured with the laboratory powder diffractometer. The single crystal structure of the hydrate of ethanol solvate of 3 - 3·0.33C2H6O·0.33H2O (3a) - is also presented. The hydrogen-bonding patterns of all compounds are discussed.

• A simple coordination complex exhibiting colour change on slight structural modification: Synthesis and crystal structures of violet and yellow forms of [NiII(opda)2(NCS)2] (opda = orthophenylenediamine)

The violet-coloured compound [NiII(opda)2(NCS)2] (1) undergoes colour change to strawyellow colour retaining its molecular composition on standing over long period of time at room temperature in the solid state. Compound 1 (violet form) and its yellow-form [NiII(opda)2(NCS)2] (2) (opda = orthophenylenediammine) have been characterized by routine spectroscopic methods and single crystal X-ray diffraction analysis. Compound 1 crystallizes in monoclinic space group $P2_1/c$ and its yellow form (compound 2) retains same space group. Their crystal structures show an intricate supramolecular network based on N-H$\cdots$S hydrogen bonds, that involve amine and thiocyanate groups coordinated to nickel(II).

• Weak C-H$\cdots$F-C interactions in carboxylate anion binding: Synthesis, spectroscopic and X-ray structural studies of [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\cdots$11H2O and [Co(phen)2CO3](C7H3NO4Cl)$\cdot$6H2O

Two new complex salts containing 2,5-substituted benzoate ions, [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\cdot$11H2O (1) and [Co(phen)2CO3](C7H3NO4Cl)$\cdot$6H2O (2) (where phen = 1,10-phenanthroline, C7H3O2FCl = 2-chloro-5-fluorobenzoate (cfbz) and C7H3NO4Cl = 2-chloro-5-nitrobenzoate(cnbz)) were synthesized by reacting carbonatobis(1,10-phenanthroline)cobalt(III) chloride with appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C-H$\cdots$F and C-H$\cdots$O interactions amid other heteroatom interactions. The complex salts have been characterized by elemental analyses, spectroscopic studies (IR, UV/Visible, multinuclear NMR), conductance and solubility product measurements. Single crystal X-ray structure determination revealed ionic structures of both the complex salts having discrete ions along with lattice water molecules. Crystal lattice is stabilized by a variety of hydrogen bonding interactions, i.e. O-H$\cdots$O, C-H$\cdots$O and C-H$\cdots$F involving second sphere coordination besides 𝜋-𝜋 interaction. Furthermore, packing analyses reveal that C-H…F interactions can manifest even in the presence of a large number of heteroatom interactions.

• Distinguishing crystallite size effects from those of structural disorder on the powder X-ray diffraction patterns of layered materials

Both crystallite size effects and structural disorder contribute to the broadening of lines in the powder X-ray diffraction (PXRD) patterns of layered materials. Stacking faults, in particular, are ubiquitous in layered materials and aside from broadening also induce peaks due to select reflections to shift away from the Bragg positions. The effect of structural disorder has to be suitably discounted before the application of the Scherrer formula for the estimation of crystallite size.

• Crystallization of copper(II) sulfate based minerals and MOF from solution: Chemical insights into the supramolecular interactions

Crystallization of solids, molecular or non-molecular from solution is a supramolecular reaction. Nucleation of a lattice structure at supersaturation can be conceived to result from a critical nucleus, a high energy intermediate (supramolecular transition state). Conceptualization of a structure for the critical nucleus in terms of aggregation of tectons through non-covalent interactions provides chemical insights into the architecture of a solid. The retrosynthetic analysis of copper-based minerals and materials offers an elegant description for the crystal packing. It addresses the influence of the geometry, functionality and reactivity of copper tecton(s) in directing a specific supramolecular aggregation. The mechanistic approach provides guiding principles to chemists to account for the experimentally crystallized solids and a platform to practice structure-synthesis correlation. Rationalization of the same composition with different atomic arrangements (polymorphs), compositional variation leading to different pseudopolymorphs, degree of hydration (anhydrous to hydrated), water clusters, role of solvent, etc. can all be justified on molecular basis. Also, the method gives predictive components including directions to synthesize new solids. In a nutshell, the paper is an attempt to generalize the crystallization of inorganic solids from solution by recognizing supramolecular interactions between metal tectons and gain insights for designing new MOF.

• Effect of metal ion doping on the photocatalytic activity of aluminophosphates

The metal ions (Ti+4, Mg+2, Zn+2 and Co+2) have been substituted in place of Al$^{+3}$ in aluminophosphates (AlPOs). These compounds were used for the first time as possible photocatalysts for the degradation of organic dyes. Among the doped AlPOs, ZnAlPO-5, CoAlPO-5, MgAlPO-11, 18 and 36 did not show any photocatalytic activity. MgAlPO-5 showed photocatalytic activity and different loading of Mg (4, 8, 12 atom % of Mg) were investigated. The activity can be enhanced by the increasing of concentration of the doped metal ions. TiAlPO-5 (4, 8, 12 atom % of Ti) showed the highest photocatalytic activity among all the compounds and its activity was compared to that of Degussa P25 (TiO2). The activity of photocatalysts was correlated with the diffuse reflectance and photoluminescence spectra.

• Journal of Chemical Sciences

Volume 132, 2019
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• Editorial Note on Continuous Article Publication

Posted on July 25, 2019