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• 182162-47-6 C₂₂H₂₄ 
• 105787-09-5 (1α,4α,4aα,7aα)-4,4a,5,6,7,7a-Hexahydro-8,8-dimethyl-1,4-diphenyl-1,4-methano-1H-cyclopenta[d]pyridazin 

Relevant academic research and scientific papers

Preferred formation of anti-housane (retention) in the sensitized photodenitrogenation of cyclopentane-annellated DBH-type azoalkanes through long-range steric effects in the cyclization of the triplet cyclopentane-1,3-diyl diradicals

The photolysis of the cyclopentene- and cyclopentane-annellated DBH-type azoalkanes 1a and 1b affords under singlet conditions (high-temperature direct photolysis) predominantly the inverted housanes syn-2 in similar amounts for both derivatives 2a and 2b

Wavelength-selective photodenitrogenation of azoalkanes to high-spin polyradicals with cyclopentane-1,3-diyl spin-carrying units and their photobleaching: EPR/UV spectroscopy and product studies of the matrix-isolated species

The photolysis of the mono-, bis-, and trisazoalkanes 1, 2, and 3 in a toluene matrix at 77 K has been studied by EPR and UV spectroscopy. The purpose was to find the optimal conditions for the generation of the corresponding organic high-spin polyradicals (the triplet diradicals D-1, D-2, and D-3, the tetraradicals T-2 and T-3, and the hexaradical H-3) all with localized cyclopentane-1,3-diyl spin-carrying units, connected by m-phenylene (except D-1) as ferromagnetic coupler. Irradiation of these azoalkanes at 333, 351, or 364 nm gave different polyradical compositions. This observed wavelength dependence is due to the secondary photoreaction (photobleaching) of the polyradical intermediate. The photobleaching process has been examined in detail for the triplet diradical D-1, for which π,π* excitation affords the cyclopentenes 5 instead of the housane 4 (the usual product of the diradical D-1 on warm-up of the matrix). The π,π*-excited diradical D-1 fragments into a pair of allyl and methyl radicals (the latter was observed by EPR spectroscopy of a photobleached sample), and recombination affords the cyclopentene. Similar photochemical events are proposed for the photobleaching of the tetraradical T-2 and hexaradical H-3, derived from the respective azoalkanes 2 and 3. Thus, photobleaching of the polyradicals competes effectively with their photogeneration from the azoalkane. This unavoidable event is the consequence of spectral overlap between the cumyl-radical π,π* chromophore of the polyradical and the n,π* chromophore of the azoalkane at the wavelength (364 nm), at which the latter is photoactive for the required extrusion of molecular nitrogen.

1,3-Diradicals Embedded in Curved Paraphenylene Units: Singlet versus Triplet State and In-Plane Aromaticity

Curved π-conjugated molecules and open-shell structures have attracted much attention from the perspective of fundamental chemistry, as well as materials science. In this study, the chemistry of 1,3-diradicals (DRs) embedded in curved cycloparaphenylene (

1,3-Cyclopentanediyl diradicals: Substituent and temperature dependence of triplet - Singlet intersystem crossing

The lifetimes of 33 1,3-diaryl-1,3-cyclopentanediyl triplet diradicals were determined by laser flash photolysis of the corresponding azoalkane precursors. The first-order decay rate constants range from 0.8 to 16.7 × 105 s-1 in degassed solution at 294 K and exhibit a systematic, but nonlinear dependence on Brown's σ+ substituent constants. Analysis of spin-orbit coupling in terms of the two-electrons-in-two-orbitals model indicates that the electronic effect on the rates of intersystem crossing operates by influencing the weight of ionic contributions in the lowest singlet state wave functions of the diradicals. Counter to intuition, but in agreement with the prediction by the model, push-pull substitution does not enhance the ionic contribution. Arrhenius parameters, Ea = 2-6 kcal mol-1 and A = 107-1010 s-1, were determined from the temperature dependences of the decay rate constants. A sensitive statistical test is used to establish that the Arrhenius parameters exhibit enthalpy-entropy compensation, that is, an approximate isokinetic relationship.

The D parameter (EPR zero-field splitting) of localized 1,3-cyclopentanediyl triplet diradicals as a measure of electronic substituent effects on the spin densities in para-substituted benzyl-type radicals

The zero-field splitting parameters D of the symmetrically disubstituted and unsymmetrically monosubstituted 1,3-diaryl-1,3-cyclopentanediyl triplet diradicals 1, 2 (X = p-MeO, p-Me, p-Cl, P-NH2, P-CO2Me, p-CN, p-NO2), and 5 were determined in 2-methyltetrahydrofuran glass at 77 K. The linear plot (m = 0.558, r2 = 0.993) of the experimental D values for the symmetrically disubstituted derivatives versus the corresponding monosubstituted ones reveals that the electronic substituent effects are additive and implies (except for the magnetic dipolar interaction) that each benzyl-type radical site acts independently in the localized diradicals. This additivity permits us to view these triplet diradicals as a composite of the two separate monoradical components and allows us to assess valuable electronic properties of benzyl-type monoradicals from the D parameter of the triplet diradical species. A theoretical analysis shows that the D parameter is a measure of the spin density p at the benzylic positions and the inter-radical distance d in localized diradicals. A good correlation exists between the D parameter of these triplet diradicals (constant inter-radical distance d) and the EPR hyperfine coupling constants of the corresponding benzyl-type monoradicals, which establishes that the observed electronic substituent effects reflect changes in the spin densities at the radical sites. The novel AZ? scale allows us to quantify spectroscopically the para substituent effect on the spin delocalization at the benzylic position.

Diastereo- and regioselective synthesis of diquinanes and related systems from tricyclo[3.3.0.02,4]octanes by chemical electron transfer (CET)

A new synthetic methodology for diquinanes by one-electron oxidation of tricyclo[3.3.0.02,4]octanes and subsequent stereocontrolled rearrangement is provided. The latter compounds are conveniently accessible through acid-catalyzed isopyrazole cycloaddition, followed by hydrogenation and photoextrusion of molecular nitrogen. The oxidative rearrangement of the tricyclooctanes proceeds catalytically and cleanly to afford regio- and diastereoselectively the corresponding diquinanes.