Spin selectivity in low temperature solid state photochemistry

Leung, Martin; El‐Sayed, M. A.

doi:10.1021/ja00836a049

Cited by 18 publications

(7 citation statements)

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“…There have been only a few reports on the sublevel selective reactions. Unequal reaction rates for the triplet sublevels were shown for the photochemical decomposition of pyrimidine and tetrazine derivatives at low temperatures. Recent studies of magnetic field effects on the radical yield using transient absorption spectroscopy clarified the influence of the SOC interaction on photoinduced electron transfer reactions in fluid solutions. − Quantitative investigations on the magnitude of the spin polarization due to SOCM may give important information not only about the interactions between the radicals but also the dissociation process of the contact radical ion pair (CRIP) or exciplex in solutions.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic Enhancement Factors of the Spin−Orbit Coupling Mechanism Polarization in the Duroquinone−N,N-Dimethylaniline Derivative Systems

et al. 1998

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Dynamics of the electron spin polarization of the quinone anion radical generated from the photoinduced electron transfer between duroquinone (DQ) and N,N-dimethylaniline (DMA) as well as its p-halogen substituents (4XDMA) has been investigated by using transient absorption and FTEPR spectroscopies. The radical yield decreased with increasing atomic number of the halogen in the donor. The intrinsic enhancement factors of net absorptive polarization due to the spin−orbit coupling mechanism (SOCM) of V SOCM = 2, 17, and 25 were determined in the unit of thermal equilibrium polarization at room temperature for the DQ-4ClDMA, DQ-4BrDMA, and DQ-4IDMA systems, respectively. The net absorptive spin polarization observed has been discussed in terms of SOC interaction of the triplet contact radical ion pair (CRIP) state with the ground state, which is coupled with the singlet CRIP states in the solvent coordinate.

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Section: Introductionmentioning

confidence: 99%

Intrinsic Enhancement Factors of the Spin−Orbit Coupling Mechanism Polarization in the Duroquinone−N,N-Dimethylaniline Derivative Systems

et al. 1998

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“…Furthermore, a 1 H NMR analysis of recovered samples showed only the starting material. It is possible that the short-lived component may arise from molecules in less rigid sites either at the surface or at defect sites, but we cannot discount that different triplet radical pair sublevels formed by state-selective intersystem crossing in the starting ketone may have access to different intersystem crossing mechanisms. − …”

Section: Resultsmentioning

confidence: 99%

Strongly Entangled Triplet Acyl–Alkyl Radical Pairs in Crystals of Photostable Diphenylmethyl Adamantyl Ketones

2021

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Radical pairs generated in crystalline solids by bond cleavage reactions of triplet ketones offer the unique opportunity to explore a frontier of spin dynamics where rigid radicals are highly entangled as the result of short interradical distances, large singlet−triplet energy gaps (ΔE ST ), and limited spin−lattice relaxation mechanisms. Here we report the pulsed laser generation and detection of strongly entangled triplet acyl−alkyl radical pairs generated in nanocrystalline suspensions of 1,1-diphenylmethyl 2-ketones with various 3-admantyl substituents. The sought-after triplet acyl−alkyl radical pairs could be studied for the first time in the solid state by taking advantage of the efficient triplet excited state α-cleavage reactions of 1,1-diphenylmethyl ketones and the slow rate of CO loss from the acyl radicals, which would have to generate highly unstable phenyl and primary alkyl radicals or relatively unstable secondary and tertiary alkyl radicals. With the loss of CO prevented, the lifetime of the triplet acyl−alkyl radical pair intermediates is determined by intersystem crossing to the singlet radical pair state, which is followed by immediate bond formation to the ground state starting ketone. Experimental results revealed biexponential kinetics with long-lived components that account for ca. 87−92% of the transient population and lifetimes that extend to the range of 53−63 μs, the longest reported so far for this type of radical pair. Structural information inferred from the starting ketone will make it possible to analyze the affects of proximity and orientation of the singly occupied orbitals and potentially help set a path for the use of triplet radical pairs as qubits in quantum information technologies.

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“…which effectively reverses (1). Although photodissociation is theoretically possible with radiation in the infrared to about 11 000 Á, chlorine nitrate is transparent at wavelengths longer than about 4600 Á.3 At altitudes above about 35 km the most important wavelengths for photolysis of chlorine nitrate are in the 2000-2200-Á range for which it has absorption cross sections of 300-400 X 10-20 cm2.…”

Section: References and Notesmentioning

confidence: 99%