Photoisomerization of a phosphorus-based biradicaloid: ultrafast dynamics through a conical intersection

Abstract

As previously reported, photoisomerization of the open-shell singlet biradicaloid [TerNP]2CNDmp yields its closed-shell housane-type isomer. In the present study, pump-probe spectroscopy was applied to investigate the excited-state dynamics of the...

A cyclic thioketone as biradical heterocyclopentane-1,3-diyl: synthesis, structure and activation chemistry

“…Since photochemical transformation into the corresponding closed-shell singlet compound 6S, so-called housanes (Scheme 1 and Fig. 3), has been observed for 5O and 5NDmp, 1,9,11,12,17 the photochemical behaviour of this biradical 5S was investigated. Quantum chemical calculations (DLPNO-CCSD(T)/def2-TZVP//PBE-D3/def2-TZVP, see ESI ‡) were first carried out to evaluate whether a minimum exists on the potential energy surface (PES) for the housane type species 6S.…”

“…That is, under irradiation, a transannular P-P bond is formed, resulting in a housane type closed-shell molecule (species 6X). 9,12,[15][16][17][18] When the irradiation is switched off, the system thermally reacts back, the P-P bond is cleaved and biradical 5X is recovered.…”

“…Phosphorus-heterocyclic species such as 1 and 5X belong to the class of open-shell singlet biradicals, 11,15,16,[18][19][20][21][22][23][24][25][26][27][28][29][30] which means that the spin density is exact zero at each point in space but yet they can be utilized as trapping reagents of highly reactive molecular fragments 31 and molecular switches [16][17][18] besides the activation of small molecules as discussed above. 9 Therefore, based on the known properties of 5O, we wanted to investigate how the molecular switching properties as well as the molecular activation chemistry change when the oxygen is formally exchanged for a sulphur atom, i.e., an analogous cyclic biradical thioketone of type 5S (Scheme 1) should be synthesized and its reactivity investigated.…”

Access to Benzo‐ and Naphtho‐Azaphospholes via C−H Bond Activation of Aryl‐Substituted Isonitriles

“…[42] This in turn represents a molecular switch, i. e., on irradiation with red light a trans-annular PÀ P bond is formed, resulting in a housane-like species 4R. [43][44][45] However, this species can thermally re-open the PÀ P bond and the biradical 2R is regenerated. Furthermore, in addition to housane formation, the biradical 2R can add another isonitrile equivalent, leading to the formation of a hetera-bicyclo[2.1.1]hexane (3R).…”

“…For example, isonitriles interact with one of the P−N bonds of 1 to form a new five‐membered biradical 2R [42] . This in turn represents a molecular switch, i. e., on irradiation with red light a trans ‐annular P−P bond is formed, resulting in a housane‐like species 4R [43–45] . However, this species can thermally re‐open the P−P bond and the biradical 2R is regenerated.…”