8,8'-Bi(8-azabicyclo[3.2.1]octane) and its oxidized forms

Long-range coupling in strained derivatives of the 2,3-diazabicyclo[2.2.1]hept-2-ene radical anion: An EPR, ENDOR and TRIPLE-resonance study

“…Following the pioneering work by Russell, long-range γand δ-couplings were reported for further semidione anions, 28 radical anions of bicyclic Z-azoalkanes, 9 rigid polycyclic derivatives of nitroxides 29,30 and alkyls. [31][32][33][34] In particular, they were observed for radical cations, in which a hydrazine 35,36 or an ethene π-system 18,23,37 is embedded in a polycyclic saturated carbon framework. By far the largest coupling constants a H( ) and a H( ) are found when the C᎐H(γ) or C᎐H(δ) bond is connected with the 2p z -axis at a spin-bearing π-centre by a chain of sp 3 -hybridized carbon atoms in a W-plan or zig-zag arrangement.…”

Nonequilibrium solvation energy by means of constrained equilibrium thermodynamics and its application to self-exchange electron transfer reactions

“…Compared with the optimized results for neutral and corresponding radical cations, we can see that the equilibrium structures of the cations differ largely from their corresponding neutral geometries and this has been stated both experimentally and theoretically. [41][42][43] Compared with N 2 H 4 structure, the open alkyl groups have little effect on the NN bond length, but the N-N bond lengths of all the three cations are shorter than the corresponding neutral species. Hydrazine radical cations have great flexibility at their nitrogens and the R 4 N 2 + prefers a roughly olefin-like geometry, with the nitrogens and the four attached carbons being coplanar and the two parallel p-orbitals interacting to form a ''three-electron bond'' including two p bonding and one antibonding p electrons.…”

“…of self-exchange ET reactions is much slower than other ET reactions in organic systems. [41][42][43][45][46][47] Based on the new nonequilibrium solvation theory developed in the present work, we have investigated self-exchange ET reactions between tetramethylhydrazine (Me 4 N 2 ), tetraethylhydrazine (Et 4 N 2 ), and tetrapropylhydrazine (nPr 4 N 2 ), and their corresponding radical cations. We calculate the inner reorganization energy l in , the solvent reorganization energy l o , as well as the ET coupling matrix element V rp .…”

“…Hydrazine radical cations have great flexibility at their nitrogens and the R 4 N 2 + prefers a roughly olefin-like geometry, with the nitrogens and the four attached carbons being coplanar and the two parallel p-orbitals interacting to form a ''three-electron bond'' including two p bonding and one antibonding p electrons. [41][42][43] Furthermore, pyramidalization at nitrogens in the anti bent R 4 N 2 + structures displaces the substituents at each nitrogen to the opposite sides of a plane across the NN bond. Further, the results show that the four nearest carbons attached to the central nitrogens are almost coplanar for the radical cations.…”

Vitamin B12 as an allosteric cofactor; dual fluorescence, hysteresis, oscillations and the selection of corrin over porphyrinThe chemistry of vitamin B12. Part 32. For part 31, see ref. 1.

“…51 Although potential-dependent hysteresis occurs in a few hemoproteins such as cytochrome cd 1 (involving a change in axial ligand and protein conformation), 52 no examples are known among protein-free metal porphyrins and only one example among other complexes, 53 but a CV study with variable sweep rate revealed that a substituted hydrazine behaved like the Cbi's in exhibiting 3 oxidation states, anomalies equivalent to hysteresis for both couples, and redox-catalysed interconvertion of forms. 54 Only the Co corrinoids have also been shown to exhibit oscillations. The observation of hysteresis in the redox reactions of Cbi's provides direct experimental evidence that the corrin structure can exist in (at least) two different conformations with different redox potentials.…”