Influence of hydrogen bonding on coordination polymer assembly

An extended dipyridyl ligand (L-1) capable of hydrogen bonding with guest species via urea functionalities has been designed and synthesised. Assembly of a silver(I) coordination polymer of L-1 is dependent on the nature of the hydrogen bond acceptor in a logical extension of the monopyridyl analogue

Structural studies of light-induced excited states

Over the past few years there has been a marked increase in the number of structural studies carried out on light-induced excited states. Until now, however, there has been no systematic approach to the irradiation of samples, which can make data collection difficult and results unreliable. This paper presents a device for mounting a laser on a CCD diffractometer; this device not only enables the collection of data without any constraints on the data collection strategy, but also simplifies alignment of the laser and can be left in place permanently

Unusual variations in the incidence of Z ' > 1 in oxo-anion structures

A series of Cambridge Structural Database studies show that ionic species generally form low Z′ structures, even in those cases where charge assisted hydrogen bonding is a key feature, e.g. oxo-anion complexes. By introducing a competing π–π stacking interaction, two oxo-anion compounds are shown to crystallise with more than one molecule in the asymmetric unit, including the first hydrogen phosphate containing structure to have Z′ > 2

Anion receptor coordination tripods capped by [9]ane-S3

A series of ruthenium(II) complexes with face-capping [9]ane-S3 ligands are described. The compounds function as supramolecular receptors for anions via three tripodally arranged 3-aminopyridine ligands. The [9]ane-S3 ligand stabilises the tripodal complexes which are more readily prepared and studied than their π-arene ruthenium(II) analogues. Pyrenyl derivative 4 displays some activity as a photophysical anion sensor but the anion response is complicated by the complexes concentration dependent emission behaviour. The receptors bind common anions in relatively polar media forming both 1:1 and 1:2 host–anion complexes with the CHanion interactions involving the thioether ring being implicated in anion binding as well as the convention NH donors

The molecular structure of a 2-aryl-1,3,2-dioxaphospholane and its coordination behaviour towards platinum(II) species; molecular structures of four platinum(II) complexes

The molecular structure of the 2-aryl-1,3,2-dioxaphospholane, 2,6-(CF 3) 2-C 6H 3-P(OCH 2) 2 (1), has been determined by single-crystal X-ray diffraction at 120 K. Its reactions with the platinum(II) dimers trans-[PtCl(μ-Cl)(PEt 3)] 2, trans-[PtCl(μ-Cl)(PPh 2Me)] 2, trans-[PtCl(μ-Cl)(PPhMe 2)] 2 and trans-[PtBr(μ-Br)(PEt 3)] 2 have been investigated using 31P NMR solution-state spectroscopy. Monomeric trans- and cis-Pt(II) complexes were formed; the molecular structures of cis-[PtCl 2(L)(PR 2R�)] (R{double bond, long}R�{double bond, long}Et (3), R{double bond, long}Ph, R�{double bond, long}Me (7)), cis-[PtBr 2L(PEt 3)] (9) and cis-[PtCl 2L 2] (10), where L = 2,6-(CF 3) 2-C 6H 3-P(OCH 2) 2, have been ascertained at 120 K. © 2009 Elsevier Ltd. All rights reserved

Crystal and molecular structures of the nido-carborane anions, 7,9- and 2,9 C₂B₉H₁₂

Deboronation of meta-carborane, closo-1,7-C2B10H12, with refluxing piperidine results in the quantitative formation of [(C5H10NH)(2)H+](nido-7,9-C2B9H12-) whose structure was determined by X-ray diffraction. Heating under vacuum liberates piperidine to give (C5H10NH2+)(nido-7,9-C2B9H12-). The reaction of meta-carborane with KOH in refluxing ethanol yields K+ nido-7,9-C2B9H12- and the cage substituted anion 10-EtO-7,9-C2B9H11-. The protonated Proton Sponge salt (PSH+)(nido-7,9-C2B9H12-) (PS=1,8-N,N,N',N'-tetramethylnaphthalenediamine) was obtained by metathesis from the potassium salt, an X-ray crystallographic study located the bridging hydrogen in the anion on the open face between the two adjacent boron atoms. Anaerobic deboronation of para-carborane, closo-1,12-C2B10H12, with KOH in refluxing tetraglyme-toluene gives the potassium salt of nido-2,9-C2B9H12- from which 2,9-C2B9H13 was isolated in 45% yield by protonation. The salt (PSH+)(nido-2,9-C2B9H12-), obtained from nido-2,9-C2B9H13 and PS, was shown by single crystal X-ray crystallography to contain a hydrogen bridging two boron atoms opposite the carbon atom on the open face. Aerobic deboronation of para-carborane with KOH forms closo-1,10-C2B8H10 and 2-HO-closo-1,10-C2B8H9 in low yields. Fully assigned multinuclear NMR (B-11,C-13 and H-1) data are reported for the isomeric 7,8-, 7,9- and 2,9-nido-C2B9H12- anions and neutral 7,8- and 2,9-C2B9H13, and compared with computed shifts (at the GIAO B3LYP/6-311G* level) from optimized (at MP2/6-31G*) geometries

Role of the hydrogen bonds in nitroanilines aggregation: Charge density study of 2-methyl-5-nitroaniline

The electron charge distribution of 2-Methyl-5-nitroaniline has been studied from high-resolution singlecrystal X-ray data at 100 K, and ab initio calculations which include X-ray structure factors computed from a superposition of ab initio molecular electron densities. Using the Hansen and Coppens' rigid pseudoatom multipolar model refinements were performed on both the experimental and the theoretical X-ray data sets from which, molecular atomic charges and dipolar moments were obtained. To understand the nature and the magnitude of the intermolecular interactions. the Atoms in Molecules theory was used to investigate the topology of the electron density of the in-crystal, both experimental interacting as well as theoretical noninteracting, and in-vacuum molecules. A meticulous analysis of the topological properties of the experimental charge density and of its Laplacian indicates, contrary to expectations, a two center character of the N-(HO)- O-. . . synthons that induce the known polar chain formation in nitroanilines and the presence of a C-methyl-H-O interaction further strengthening the chains. It also shows the attractive nature of the rather strong C-(HO)-O-. . . interactions that help the head-to-tail arrangement of the chains. They build two intermolecular six membered hydrogen bonded rings, embracing a N-(HO)-O-. . . interaction, that originate centrosymmetric dimers which impair the macroscopic second harmonic generation of the title compound. The authenticity of a previously proposed closed shell C-aryl-H(. . .)pi interaction between adjacent chains has been confirmed. The latter has not been observed in m-nitroaniline, 2-methyl-4-aniline or other related compounds with chains built from similar N-(HO)-O-. . . synthons and assembled head-to-head. Crystallization causes a molecular electric dipolar moment higher than that of the free molecule, the latter being coincident with the experimental value in solution, and with the one calculated from the refinement of the theoretical X-ray data. It also induces changes in the charge density distribution and its topology, and an enhancement of the intramolecular conjugation that can be related to a molecular aggregation mechanism ruled by the N- (HO)-O-. . . synthon. These findings strongly point to the existence of cooperative effects

Tetrakis 3,5-bis-(trifluoromethyl)phenyl silane

The title compound, tetra­kis[3,5-bis­(trifluoro­meth­yl)phen­yl]silane (SiAr'''4, C32H12F24Si), is a minor product from the reaction of silicon(IV) bromide with lithia­ted 1,3-bis­(trifluoro­meth­yl)benzene (Ar'H). The structure crystallizes with two half-mol­ecules in the asymmetric unit, with each central Si atom positioned on a twofold axis in a pseudo-tetra­hedral environment, with Si-C bond lengths in the range 1.873 (3)-1.879 (3) Å