Exploring Two-State Reactivity Pathways in the Cycloaddition Reactions of Triplet Methylene

Measurement of time dependent product branching ratios indicates two-state reactivity in metal mediated chemical reactions

For several decades, the influence of Two State Reactivity (TSR) has been implicated in a host of reactions, but has lacked a stand-alone, definitive experimental kinetic signature identifying its occurrence. Here, we demonstrate that the measurement of a temporally dependent product branching ratio is indicative of spin inversion and is a kinetic signature of TSR. This is caused by products exiting different hypersurfaces with different rates and relative exothermicities. The composite measurement of product intensities with the same mass but with different multiplicities yield biexponential temporal dependences with the sampled product ratio changing in time. These measurements are made using the single photon initiated dissociative rearrangement reaction (SPIDRR) technique which identifies TSR but further determines the kinetic parameters for reaction along the original ground electronic surface in competition with spin inversion and its consequent TSR.

Philicity indices within the spin-polarized density-functional theory framework

The electrophilicity index is analyzed within the framework of spin-polarized density-functional theory. In this context, constrained philicities, omega(N) identical with (mu(N))(2)(2eta(NN)), are introduced in order to define the capability of a system to acquire or donate electrons in a process at constant spin number. The spin-philicity/spin-donicity indices, omega(S)(+/-) identical with (mu(S) (+/-))(2)(2eta(SS)), are examined and rationalized here as the philicity of a given system to change its spin-polarization state, as being defined through the spin potential mu(S) and spin hardness eta(SS) for a process at constant number of electrons. The local extension of these indices has been also outlined and numerical results have been discussed on the analysis of the electrophilic nature of some simple carbene systems both in the singlet and triplet states.