Understanding the Properties of Inorganic Benzenes Based on π-Electron Densities

Dithiophene-Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics

Access to dithiophene-fused oxadiborepins and the first azadiborepins attained via a modular synthesis route are presented. The new compounds emit intense blue light, some of which demonstrate fluorescence quantum yields close to unity. Cyclic voltammetry (CV) revealed electrochemically reversible one-electron reduction processes. The weak aromatic character of the novel 1,2,7-azadiborepin ring is demonstrated with in-depth theoretical investigations using nucleus-independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations.

Pnictogen-Silicon Analogues of Benzene

Since the discovery of the first "inorganic benzene" (borazine, B3N3H6), the synthesis of other noncarbon derivatives is an ongoing challenge in Inorganic Chemistry. Here we report on the synthesis of the first pnictogen-silicon congeners of benzene, the triarsa- and the triphospha-trisilabenzene [(PhC(NtBu)2)3Si3E3] (E = P (1a), As (1b)) by a simple metathesis reaction. These compounds are formed by the reaction of [Cp″2Zr(η(1:1)-E4)] (E = P, As; Cp″ = C5H3tBu2) with [PhC(NtBu)2SiCl] in toluene at room temperature along with the silicon pnictogen congeners of the cyclobutadiene, [(PhC(NtBu)2)2Si2E2] (E = P (2a), As (2b)), which is unprecedented for the arsenic system 2b. All compounds were comprehensively characterized, and density functional theory calculations were performed to verify the stability and the aromatic character of the triarsa- and the triphospha-trisilabenzene.

Dehydrocoupling and Silazane Cleavage Routes to Organic-Inorganic Hybrid Polymers with NBN Units in the Main Chain

Despite the great potential of both π-conjugated organoboron polymers and BN-doped polycyclic aromatic hydrocarbons in organic optoelectronics, our knowledge of conjugated polymers with B-N bonds in their main chain is currently scarce. Herein, the first examples of a new class of organic-inorganic hybrid polymers are presented, which consist of alternating NBN and para-phenylene units. Polycondensation with B-N bond formation provides facile access to soluble materials under mild conditions. The photophysical data for the polymer and molecular model systems of different chain lengths reveal a low extent of π-conjugation across the NBN units, which is supported by DFT calculations. The applicability of the new polymers as macromolecular polyligands is demonstrated by a cross-linking reaction with Zr(IV) .

Electron Density Analysis of Hyperconjugation

Hyperconjugation is analyzed through the electron density of orbitals responsible for hyperconjugative interactions, which cannot be detected by means of conventional electron-density-based calculations. This interaction is detected through the π electron density topology, by excluding σ electron density from the total. As the presence of the hyperconjugation phenomenon in carbocation systems is well understood, several carbocations are benchmarked, and the results show that the positive carbon atom establishes a hyperconjugative critical point with the adjacent methyl group(s). Also, π localization and delocalization indices are employed to support the conclusions made by the topological analysis.