Sequential radical and cationic reactivity at separated sites within one molecule in solution.

Distonic radical cations (DRCs) with spatially separated charge and radical sites are expected to show both radical and cationic reactivity at different sites within one molecule. However, such "dual" reactivity has rarely been observed in the condensed phase. Herein we report the isolation of crystalline 1λ2,3λ2-1-phosphonia-3-phosphinyl-cyclohex-4-enes 2a,b˙+, which can be considered delocalized DRCs and were completely characterized by crystallographic, spectroscopic, and computational methods. These DRCs contain a radical and cationic site with seven and six valence electrons, respectively, which are both stabilized via conjugation, yet remain spatially separated. They exhibit reactivity that differs from that of conventional radical cations (CRCs); specifically they show sequential radical and cationic reactivity at separated sites within one molecule in solution.

The case of a µ2-P aromatic phosphinine as a 4-electron donor forming σ- and π-three-center-two-electron bonds.

Profound insight into the electronic structures of occasionally observed µ2-P bridging phosphinines remains limited. In this work, we present the isolation and X-ray crystallographic characterization of a dimeric Rh(I) phosphinine complex exhibiting both η1-P and µ2-P phosphinine coordination modes. Variable temperature NMR analyses and DOSY spectrum measurement confirmed the presence of two types of fluxional phenomena in solution: η1-P phosphinine bonding and dissociation, and η1-P and µ2-P equilibrium. DFT calculations in conjunction with single crystal X-ray diffraction studies suggest that the µ2-P phosphinines donate four electrons via a σ-lone pair and a high-lying π-type electron pair, instead of two σ-lone pairs, forming σ- and π-three-center-two-electron bonds. The stronger π-type interactions lead to longer P-C bonds and larger negative coordination chemical shifts for µ2-P phosphinines. However, the binding interactions of µ2-P are thermodynamically weaker than those of η1-P. Reactivity studies further confirm the labile nature of the µ2-P phosphinine bonds, which could be easily converted to an η1-P phosphinine.

Room temperature stable E,Z-diphosphenes: their isomerization, coordination, and cycloaddition chemistry.

E,Z-isomers display distinct physical properties and chemical reactivities. However, investigations on heavy main group elements remain limited. In this work, we present the isolation and X-ray crystallographic characterization of N-heterocyclic vinyl (NHV) substituted diphosphenes as both E- and Z-isomers (L[double bond, length as m-dash]CH-P[double bond, length as m-dash]P-CH[double bond, length as m-dash]L, E,Z-2b; L = N-heterocyclic carbene). E-2b is thermodynamically more stable and undergoes reversible photo-stimulated isomerization to Z-2b. The less stable Z-isomer Z-2b can be thermally reverted to E-2b. Theoretical studies support the view that this E ↔ Z isomerization proceeds via P[double bond, length as m-dash]P bond rotation, reminiscent of the isomerization observed in alkenes. Furthermore, both E,Z-2b coordinate to an AuCl fragment affording the complex [AuCl(η2-Z-2b)] with the diphosphene ligand in Z-conformation, exclusively. In contrast, E,Z-2b undergo [2 + 4] and [2 + 1] cycloadditions with dienes or diazo compounds, respectively, yielding identical cycloaddition products in which the phosphorus bound NHV groups are in trans-position to each other. DFT calculations provide insight into the E/Z-isomerisation and stereoselective formation of Au(i) complexes and cycloaddition products.

[Determination of relative error of pressure-broadening linewidth for the experimentally indistinguishable overlapped spectral lines with Voigt profile].

The simulation and fitting of the overlapped spectral lines with Voigt profile were presented in this paper. The relative errors epsilon of the fitted pressure-broadening linewidth when taking the overlapped spectral line as one spectrum were discussed in detail. The relationship between such error and the two spectral lines center distance deltav0, and theoretical pressure-broadening linewidth deltav(L)0 were analyzed. Epsilon is found to be very large and the relationship between epsilon and deltav0, deltav(L)0 is very complicated when the value of pressure-broadening linewidth is considerably less than that of Dopplerian one deltavD. When deltav(L)0 is comparative to deltaVD the relationship between epsilon and deltav0 is close to the smooth two-order polynomial curve. However, the slop of this curve is negative while deltav(L)0 is smaller than deltavD and is positive when larger. Generally, epsilon decreases with the increase of proportion of deltav(l)0 to the whole spectral linewidth. All the above conclusion and corresponding data are the significant reference to determine the precise pressure-broadening coefficient from the experimentally indistinguishable overlapped spectrum, as well as to correct the fitted pressure-broadening linewidth.