Novel class of heterometallic cubane and boride clusters containing heavier group 16 elements

Thermolysis of an in situ generated intermediate, produced from the reaction of [Cp*MoCl4] (Cp* = η5-C5Me5) and [LiBH4.THF], with excess Te powder yielded isomeric [(Cp*Mo)2B4TeH5Cl] (2 and 3), [(Cp*Mo)2B4(μ3-OEt)TeH3Cl] (4), and [(Cp*Mo)4B4H4(μ4-BH)3] (5). Cluster 4 is a notable example of a dimolybdaoxatelluraborane cluster where both oxygen and tellurium are contiguously bound to molybdenum and boron. Cluster 5 represents an unprecedented metal-rich metallaborane cluster with a cubane core. The dimolybdaheteroborane 2 was found to be very reactive toward metal carbonyl compounds, and as a result, mild pyrolysis of 2 with [Fe2(CO)9] yielded distorted cubane cluster [(Cp*Mo)2(BH)4(μ3-Te){Fe(CO)3}] (6) and with [Co2(CO)8] produced the bicapped pentagonal bipyramid [(Cp*MoCo)2B3H2(μ3-Te)(μ-CO){Co3(CO)6}] (7) and pentacapped trigonal prism [(Cp*MoCo)2B3H2(μ3-Te)(μ-CO)4{Co6(CO)8}] (8). The geometry of 8 is an example of a heterometallic boride cluster in which five Co and one Mo atom define a trigonal prismatic framework. The resultant trigonal prism core is in turn capped by two boron, one Te, and one Co atom. In the pentacapped trigonal prism unit of 8, one of the boron atoms is completely encapsulated and bonded to one molybdenum, one boron, and five cobalt atoms. All the new compounds have been characterized in solution by IR, 1H, 11B, and 13C NMR spectroscopy, and the structural types were unambiguously established by crystallographic analysis of 2 and 4–8

Catecholboryl-functionalized ferrocene based Lewis acid system: a selective probe for fluoride ion through multiple channels

The design and synthesis of two new receptors, C₂₀H₁₉O₃BFe and C₂₀H₂₁O₃BFe and their anion sensing properties through multiple channels are reported. Both the receptors, having chelating boronic ester Lewis acidic centre as the sole binding site, selectively bind fluoride ion in micromolar concentration. The binding constant of C₂₀H₁₉O₃BFe with the fluoride ion has been found to be quite high [K = 106 M⁻¹], whereas it displays a negligible affinity towards other effective competitors, for example acetate and cyanide (K = 10 M₋₁) and no sensitivity towards other halide ions. Upon selective recognition of F⁻ in acetonitrile, the redox potential of C₂₀H₁₉O₃BFe shifted by ΔE = 200 mV and the fluorescence emission was quenched drastically. The considerable changes in their absorption spectra are accompanied by the appearance of a new low energy (LE) peak at 566 nm and by a strong colour change from yellow to deep green which allows the prospective for “naked eye” detection of F⁻ anion

Novel Class of Heterometallic Cubane and Boride Clusters Containing Heavier Group 16 Elements

Thermolysis of an in situ generated intermediate, produced from the reaction of [Cp*MoCl₄] (Cp* = η⁵-C₅Me₅) and [LiBH₄.THF], with excess Te powder yielded isomeric [(Cp*Mo)₂B₄TeH₅Cl] (<b>2</b> and <b>3</b>), [(Cp*Mo)₂B₄(μ₃-OEt)­TeH₃Cl] (<b>4</b>), and [(Cp*Mo)₄B₄H₄(μ₄-BH)₃] (<b>5</b>). Cluster <b>4</b> is a notable example of a dimolybdaoxatelluraborane cluster where both oxygen and tellurium are contiguously bound to molybdenum and boron. Cluster <b>5</b> represents an unprecedented metal-rich metallaborane cluster with a cubane core. The dimolybdaheteroborane <b>2</b> was found to be very reactive toward metal carbonyl compounds, and as a result, mild pyrolysis of <b>2</b> with [Fe₂(CO)₉] yielded distorted cubane cluster [(Cp*Mo)₂(BH)₄(μ₃-Te)­{Fe­(CO)₃}] (<b>6</b>) and with [Co₂(CO)₈] produced the bicapped pentagonal bipyramid [(Cp*MoCo)₂B₃H₂(μ₃-Te)­(μ-CO)­{Co₃(CO)₆}] (<b>7</b>) and pentacapped trigonal prism [(Cp*MoCo)₂B₃H₂(μ₃-Te)­(μ-CO)₄{Co₆(CO)₈}] (<b>8</b>). The geometry of <b>8</b> is an example of a heterometallic boride cluster in which five Co and one Mo atom define a trigonal prismatic framework. The resultant trigonal prism core is in turn capped by two boron, one Te, and one Co atom. In the pentacapped trigonal prism unit of <b>8</b>, one of the boron atoms is completely encapsulated and bonded to one molybdenum, one boron, and five cobalt atoms. All the new compounds have been characterized in solution by IR, ¹H, ¹¹B, and ¹³C NMR spectroscopy, and the structural types were unambiguously established by crystallographic analysis of <b>2</b> and <b>4</b>–<b>8</b

Temperature-Assisted Molecular Reordering in n-Type Organic Semiconductor Films: The Impact on Nanoscale Morphology, Photophysical Properties, and Electron Transport

Charge carrier transport in bulk organic semiconductors, especially in solution-grown films, is invariably dictated by the semiconductor layer morphology and molecular level organization of the charge hopping centers. Therefore, even tiny positional displacements of molecules will lead to significant changes in the bulk carrier transport. Various pre- and postfilm deposition techniques have been developed to achieve the ideal layer morphology and molecular arrangement on desired substrates. Herein, to demonstrate the findings on temperature-assisted morphological restructuring initiated by molecular scale reordering of n-type molecular semiconductors, a series of positional isomers of end-substituted naphthalene diimide (NDI) derivatives were subjected to study. For one derivative, namely, m-picolylnaphthelenediimide (m-PyNDI), a dramatic improvement in field-effect electron mobility and overall device performance was observed upon postdeposition thermal treatment. To elucidate the mechanism behind this drastic change, a bottom-up approach of tracing the assembly pathways from molecular scale aggregates in solution to bulk films was carried out and systematically summarized. Spectroscopic signatures of the aggregates were carefully studied by following the exciton coupling model, and the evolution of the morphological transformation was monitored using microscopic techniques