Elucidating the Relationship between Multiradical Character and Predicted Singlet Fission Activity

Abstract

The diradical and multiradical characters of a large and diverse set of 241 predicted singlet fission candidates are determined by multiconfigurational wavefunction methods, specifically natural orbital occupation number (NOON) analysis using the CASSCF method. The ascertained multiradical character strongly supports the current prediction that a good singlet fission candidate, independent of its structure, will tend to be of the weak biradicaloid class as well as having very little tetraradical character. Although the rule remains robust, it is not absolute as a small portion of our potential candidates are predicted to be closed shell. Additionally, a smaller handful of outliers with apparent tetraradical characters are identified, suggesting there may be the possibility, albeit rare, of singlet fission amongst weak tetraradicaloids.

Near‐Infrared Lasing in Four‐Zigzag Edged Nanographenes by 1D versus 2D Electronic π‐Conjugation

“…Diradicaloid molecules have been proposed as good candidates hosting singlet exciton fission processes, which could be mediated by CT states before yielding the diradicaloid stabilized triplets. [ 32 ] Note that the outcome of those FT‐DFT calculations predicts a higher diradicaloid character for PP‐Ar than for TT‐Ar, and for TT‐Ar than for AA‐Ar, in agreement with extended zigzag edges. Quantitatively speaking, we define the (poly)radicaloid character of any compound by the index (y 0 , y 1 ) arising from the fractional occupation (y i ) of the LUMO and LUMO+1 orbitals, respectively.…”

High-throughput virtual screening for organic electronics: a comparative study of alternative strategies

“…After expanding the library of predicted SF compounds, 37 a follow-up screening which evaluated the diradical character of the potential candidates showed markedly that the biradicaloid characteristic was well-preserved among the vastly different molecules, but not all of them. 408 Indeed, it is fairly frequent to discover exceptions to the established rules when large datasets are considered and occasionally one finds that the known rules are not valid in a statistical sense. For example, it seems that there is a complete lack of correlation between computed donor–acceptor character in a dye and its efficiency in a dye sensitised solar cell.…”

High‐Fidelity Dimerization of Xanthenyl Radicals and Dynamic Qualities of a Congested Ethane: Diethyl Dixanthenyl‐9,9′‐Dicarboxylate

“…Carbon‐centered radicals have historically been labelled as short‐lived, highly reactive species due to their tendency for hydrogen‐atom abstraction, disproportionation, and aerial oxygenation. Sustained effort over recent decades has produced guiding principles that control the reactivity of carbon‐centered radicals, [1,2] which has revealed the utility of the unpaired electron for applications such as energy storage and battery materials, [3,4] spin labelling and EPR imaging, [5,6] magnetic memory, [7,8] and singlet fission‐based solar energy capture [9,10] . The growing field of dynamic covalent chemistry has recently capitalized on the controlled association and dissociation equilibrium of stable carbon‐centered radicals and their dimers, as generically represented in Figure 1a [11] .…”