Nonconventional driving force for selective oxidative C-C coupling reaction due to concurrent and curious formation of Ag0.

Is it possible to 'explore' metal's intrinsic property-a cohesive interaction-which naturally transform M0 into an aggregate or a particle or film for driving oxidative C-C bond formation? With this intention, reduction of [Ag(NH3)2]+ to Ag0 with concurrent oxidation of different phenols/naphthols to biphenyls was undertaken. The work is originated during careful observation of an undergraduate experiment-Tollens' test-where silver mirror film deposition takes place on the walls of borosilicate glass test tube. When the same reaction was carried out in polypropylene (plastic-Eppendorf) tube, we observed aggregation of Ag0 leading to floating Ag-particles but not silver film deposition. This prompted us to carry out challenging cross-coupling reaction by ONLY changing the surface of the reaction flask from glass to plastic to silicones. To our surprise, we observed good selective oxidative homo-coupling on Teflon surface while cross-coupling in Eppendorf vial. Thus, we propose that the formation of biphenyl is driven by the macroscopic growth of Ag0 into [Ag-particle] orchestrated by Ag…Ag cohesive interaction. To validate results, experiments were also performed on gram scale. More importantly, oxidation of ß-naphthol carried out in quartz (chiral) tube which yielded slight enantioselective excess of BINOL. Details are discussed.

Water-Assisted Self-Aggregation of Benzimidazole and Triazole Adducts.

The manuscript revolves around an interesting observation of solidification of a solution of N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl)-1H-1,2,3-triazole-4-yl)methyl)aniline (A6) in the NMR tube after around 12 h. Real-time images showed fibrillar and spherulitic growth with tip branching and side branching, which is thermoreversible. The compound under investigation is unique because it is synthesized to understand the anticancer activity with two pharmacophores, benzimidazole and triazole. Click chemistry is employed for in situ generation of triazole moiety on benzimidazole. Previously, benzimidazole-based compounds have shown self-aggregation-induced gel-like behavior because of hydrogen bonding and/or π-π stacking interactions. In the present case, NMR titrations with D2O addition showed two distinct changes in the chemical shift for methylene bridges (connecting benzimidazole and triazole ring) and ortho protons of the phenyl ring (attached to triazole ring). Interestingly, a single-crystal X-ray structure shows the absence of hydrogen bonds and π-π stacking while in the presence of only two distinct close contacts, completely correlating NMR data discussed in detail. A similar "molecular origin" for self-aggregation is observed in seven other flexible but regioisomeric compounds, which were designed and synthesized for inducing hydrogen bonding through the removal of N-ethyl group and insertion of aniline and/or fluoro group.

Back-Bonding Signature with High Pressure: Raman Studies on Silver Nitroprusside.

In centrosymmetric molecules, like An+[M(CN)6]n- (where A is alkali metal cation), normally all stretching vibrations of cyanide (CN-) shift to high frequency in response to nonhydrostatic pressure, whereas, in non-centrosymmetric molecules in which one axial CN ligand is replaced by NO ligand, one observes unusual softening of only equatorial CN stretching modes. This effect is pronounced when A+ is replaced by Ag+ with difference in coordination ability of latter, resulting in expression of characteristic signature of back-bonding. One can correlate this uneven stretching of cyanide to Poisson-like effect, where the axial Fe-N, Fe-C, and C-N stretching modes harden but the equatorial C-N stretching modes soften due to expansion at the equatorial plane. Thus, the present study is focused on results of non-hydrostatic high-pressure Raman measurements on silver nitroprusside up to 11.5 GPa, for not only observing characteristic signature of "back-bonding" interaction, rarely featured in literature, but also for generating reversible flexible structures akin to noncovalent interaction.

Accommodative Behavior of Non-porous Molecular crystal at Solid-Gas and Solid-Liquid Interface.

Molecular crystals demonstrate drastically different behavior in solid and liquid state, mainly due to their difference in structural frameworks. Therefore, designing of unique structured molecular compound which can work at both these interfaces has been a challenge. Here, we present remarkable 'molecular' property by non-porous molecular solid crystal, dinuclear copper complex (C6H5CH(X)NH2)2CuCl2, to reversibly 'adsorb' HCl gas at solid-gas interface as well as 'accommodate' azide anion at solid-liquid interface with crystal to crystal transformation. The latter process is driven by molecular recognition, self-assembly, and anchimeric assistance. The observed transformations are feasible due to breathing of inner and outer coordination sphere around metal center resulting in change in metal polyhedra for 'accommodating' guest molecule. These transformations cause changes in optical, magnetic, and/or ferroelectric property offering diversity in 'sensing' application. With the proposed underlying principles in these exceptional reversible and cyclic transformations, we prepared a series of compounds, can facilitate designing of novel multifunctional molecular materials.

Single crystal X-Ray structure of BeF2: α-quartz.

We report for the first time, the synthesis and X-ray diffraction studies of single crystals of BeF(2). The crystals were obtained during the sublimation of amorphous BeF(2) under static reduced pressure. BeF(2) crystallizes in the chiral trigonal space group P3(1)21. A single-crystal X-ray diffraction study on these crystals shows that each of the Be atoms is bonded to four F atoms, and each of the F atoms is bonded to two Be atoms with associated Be-F bond distances of 1.5420(13) and 1.5471(13) Å, showing an almost regular tetrahedron. The infrared spectrum of these crystals recorded at room temperature shows distinct peaks around 770 and 410 cm(-1).

Studies on TMPD:TCNB; a donor-acceptor with room temperature paramagnetism and n-pi interaction.

A donor-acceptor compound based on N,N,N',N'-tetramethyl-p-phenylene-diamine and 1,2,4,5-tetracyanobenzene (TMPD:TCNB) has been synthesized. The crystal structure of the black 1:1 complex formed between TMPD and TCNB has been determined by single crystal X-ray diffraction at room temperature. The compound crystallizes in the triclinic space group P-1 with cell dimensions: a = 7.4986(15) å, b =7.6772(11) å, c = 8.0764(15) å, alpha = 78.822(12) degrees, beta = 83.3779(19) degrees, gamma = 86.289(17) degrees .TMPD and TCNB molecules are stacked alternately in infinite columns along the a-axis. The structure does not seem to show the usual pi-pi interaction between the two aromatic rings, but indicates an n-pi interaction localized between the nitrogen atoms of the donor and the cyano groups of the acceptor.

A Three-Dimensional Ferrimagnet with a High Magnetic Transition Temperature (TC ) of 53 K Based on a Chiral Molecule.

The transparent, double bridged-(R)-spiral three-dimensional polymeric complex K0.4 [Cr(CN)6 ][Mn(S)-pn](S)-pnH0.6 ((S)-pn=(S)-1,2-diaminopropane) has been synthesized and characterized (see X-ray structure; Cr: brown, Mn: red, C: gray, N: blue, K: green). Magnetic measurements on the complex show that the MnII and CrIII ions interact ferrimagnetically and magnetic transition occurs at 53 K (Curie temperature).