Recent advances in spin chemistry

Abstract

Abstract:The great success in controlling chemical reactivity by spin manipulation was achieved in the last decade, and many remarkable spin and magnetic phenomena have been discovered. Among those discoveries, the most chemically important highlights are magnetic isotope effect, spin catalysis, and single-spin tunneling spectroscopy. This paper summarizes recent advances in these new and hot areas of modern chemistry. GENERAL OUTLOOK OF SPIN CHEMISTRYSpin chemistry as a new land and hot area in modern chemistry is based on the universal and fundamental principle-all chemical reactions are spin selective. They allowed only for those spin states of products whose total electron spin is identical to that of reagents. The reactions are forbidden if they require a change of spin.Some typical examples of spin-selective reactions are given below. The recombination of radicals into the diamagnetic molecule is allowed from singlet state of the reaction precursor, radical pair:Triplet state is strictly forbidden for the reaction, so that triplet pair either dissociates to free radicals, or experiences spin conversion (shown by dashed arrow), which transforms nonreactive triplet state into the chemically reactive singlet state.Chemical addition of radical to triplet molecule (oxygen, for instance), as well as physical quenching of excited triplet molecule by radical, takes place only in doublet state:Quartet spin state is forbidden to react and quartet-doublet spin conversion is required to switch over the reaction channel. Again, spin selectivity is controlled by competition between the dissociation of the quartet pair on the starting reagents and spin transformation of the pair into the reactive doublet state.In the reaction of two triplets (recombination of carbenes, delayed fluorescence from the fusion of two excited triplet molecules, etc.) only one of the nine spin states is open to react: *Plenary lecture presented at the 15

Identification of sources and formation processes of atmospheric sulfate by sulfur isotope and scanning electron microscope measurements

“…Of these, the surface reaction model of Lasaga et al [2008] and the well-established MIE [Buchachenko, 2000] are the only reactions that would apply to heterogeneous reactions (MIE also to gas phase), but we suggest that it is possible to rule these out as viable candidates for our observations. There is presently no clear experimental evidence to support the reaction model of Lasaga et al [2008] and there is also discussion in the literature [e.g., Balan et al, 2009] that disputes this mechanism.…”

“…KIE that have been suggested to be mass-independent include those associated with surface reaction effects [Lasaga et al, 2008], spin coupling (magnetic isotope effects (MIE)) [Buchachenko, 2000], symmetry [Gao and Marcus, 2001], self-shielding [e.g., Lyons 2008], or chance vibronic overlap of excited Romero and Thiemens [2003].…”

Mercury isotope fractionation during liquid–vapor evaporation experiments

“…Magnetic pairs are therefore also more probable to recombine into the starting molecules, while nonmagnetic pairs are more likely to form reaction products via dissociation of RÁÁR into free radicals. Due to the difference in the rates of spin conversion, isotopes with magnetic and nonmagnetic are separated and accumulation of magnetic versus nonmagnetic isotopes can be generated in products and reactants (Buchachenko, 1995;Buchachenko, 2000;Buchachenko, 2001).…”

Treatise on the Resolution of the diamond problem after 200 years

“…The Woodward-Hoffman Rule determines that the broken carbon bonds would preserve their symmetry and undergo related faster kinetic of re-graphitizing by symmetrically compatible and already existing sp 2 orbitals to reform the graphitic precursor rather than the slower pathways of rehybridization for bond rearrangement for forming different sp 3 orbitals of different symmetry for diamond formation. But, here the Resolution demonstrates a high spin asymmetric bottleneck for radical carbon, ferrometal and hydrogen radicals by the intrinsic magnetism and the enhancement by external magnetization for disrupting orbital symmetry during bond rearrangement, thereby preventing graphitization, enhancing transformation of graphitic sp 2 carbon to sp 3 carbon, and substantially lowering the sp 3 bosonic bonding interactions between carbon atoms so the sp 3 carbon atoms can accumulate and densify for greater probability of bulk (macro) high spin sp 3 [39,40] on photochemistry [41,42], on radical recombination [43,44], on spin chemistry [45], on spin catalysis [46,47] and on spin isotope effects [48]. The Little Effect is distinct from these prior spin phenomena.…”

“…The radical pair effect considers just the dynamics between two radicals. Whereas the spin chemistry of Turro [43], Buchachenko [45], and Hayashi [44] are more limited to spin itself, the Little Effect differs in its determination of spin alteration of orbital subshell and shell dynamics. The Little Effect is multi-radical phenomena and it determines novel orbital, subshell, shell and even atomic and molecular dynamics due to dense spins and energy.…”