Cation strong coupling

In contrast, SnH4+ gives two distinct cations at 77 K, one with two strongly coupled protons (lb) but the other (II), having only one strongly coupled proton. 

Thus the 2,4-dinitrophenyldiazonium cation will couple with PhOMe and the 2,4,6-compound with even the hydrocarbon 2,4,6-trimethylbenzene (mesitylene). Diazonium cations exist in acid and slightly alkaline solution (in more strongly alkaline solution they are converted first into diazotic acids, PhN=N—OH, and then into diazotate anions, PhN=N—O ) and coupling reactions are therefore carried out under these conditions, the optimum pH depending on the species being attacked. With phenols this is at a slightly alkaline pH as it is PhO , and not PhOH, that undergoes attack by... 

The radical cation (19 " ) of the strained bicyclo[2.1.0]pentane also has a puckered conformation, supported by one strongly coupled (flagpole) proton (flsyn = 4.49 mT). Ab initio calculations indicate that the transannular bond retains some bonding and that the bridgehead carbons remain pyramidal. ... 

The third radical cation structure type is the cyclohexane-1,4-diyl radical cation (22 +) derived from 1,5-hexadiene. The free electron spin is shared between two carbons, which may explain the blue color of the species ( charge resonance). Four axial p and two a protons are strongly coupled (a = 1.19 mT, 6H). + ... 

The key feature of the NMR spectra of 91 is its simplicity. Thus the 13C NMR spectrum consists of only two resonances at 4.9 and 17.6 ppm, indicating either a symmetrical trishomocyclopropenium cation, 93, or rapid equilibration between three equivalent structures (Scheme 37). The positions of the 13C NMR resonances of the cation strongly suggested the formulation of its structure as the trishomocyclopropenium ion, 93210. This conclusion was reinforced by the preparation of the deuterated cation and examination of the isotopic perturbation of its 13C chemical shifts208 211, and measurement of the 13C H coupling constants209. 

The present analysis relies on - and extends - the comprehensive theoretical study of Refs. [23,24] on the multi-state interactions in the manifold of the X — E states of Bz+. Like this recent work, it utilizes an ab initio quantum-dynamical approach. In Refs. [23,24] we have, in addition, identified strong coupling effects between the B — C and B — D electronic states, caused by additional conical intersections between their potential energy surfaces. A whole sequence of stepwise femtosecond internal conversion processes results [24]. Such sequential internal conversion processes are of general importance as is evidenced indirectly by the fluorescence and fragmentation dynamics of organic closed-shell molecules and radical cations [49,50]. It is therefore to be expected that the present approach and results may be of relevance for many other medium-sized molecular systems. 

The two distinct types of interlayer reaction observed in the MPS3 componnds (electron transfer to the layers and ion transfer from the layers into the reactant solution) are partially reversible and occur with simultaneous intercalation of catioiuc species into the interlayer spaces. The balance between the two different reaction pathways appears to depend on the band gap of the particular solid. Ion transfer reactions are easier in the larger band gap compounds (for example, with M = Zn, Cd, and Mn) where the layers appear to behave as cations weakly coupled to P2S6 units. The MPS3 lattices behave very differently from the dichalcogenides where the strong covalent interactions between formally M + cations and anions preclude any ion transfer chemistry involving the layers. 

The ESR spectrum of ethane radical cation at 4 K in SFe contained a 1 2 1 triplet because of two strongly coupled protons (15.25 mT), corresponding to a spin-... 

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