Diindenoanthracene Diradicaloids Enable Rational, Incremental Tuning of Their Singlet-Triplet Energy Gaps

Abstract

Haley and co-workers report the synthesis and physical characterization of a family of diradicaloids on the basis of the diindenoanthracene framework. Computations suggested that altering the external fused rings on both sides of the pentacyclic core would yield systematic changes in their open-shell properties, results that have been corroborated experimentally. This structure refinement approach provides a deeper understanding on how to tune the intrinsic properties of diradicaloid compounds in a rational and predictable manner.

Modulating the ground state, stability and charge transport in OFETs of biradicaloid hexahydro-diindenopyrene derivatives and a proposed method to estimate the biradical character

“…The same trend is obtained for DIAn derivatives. 16 Compared to FF derivatives, surprisingly, the HDIP derivatives have an index y 0 slightly reduced by 0.02 except for syn-HDIP for which the reduction is more important (0.05) even if the bond b is genuinely longer for HDIP derivatives than that obtained for FF derivatives. A longer bond b for HDIP derivatives can be attributed to the steric repulsion between the aliphatic bridge and the ethynyl function.…”

“…Due to the presence of free radicals, the magnetic susceptibilities of HDIP derivatives show much higher paramagnetic susceptibilities than that usually obtained from the contribution of the excited triplet state, precluding the estimation of the DE S-T (see ESI †). 7, 11,13,16 X-ray crystallographic analysis Fortunately, for all the compounds, single crystals suitable for crystallography analysis were obtained by recrystallization (reliability factor (R) less than 0.06 for linear-HDIP and less than 0.05 for the others). For HDIP, linear-and anti-HDIP, the crystals have a triclinic symmetry with the P 1 space group, whereas for syn-HDIP the crystals have a monoclinic symmetry with the P2 1 / c space group.…”

“…The trend of DE S-T values for HDIP derivatives is different from that observed recently in dibenzo-DIAn derivatives which possess the anthracene central core and the mesityl group at the apical position. 16 However, they are not strictly comparable since HDIP derivatives have the TIPS-ethynyl group at the apical position and two aliphatic bridges at the central core. Since the DE S-T of native FF follows the reverse trend of the biradical character according to the calculation (see ESI †), the functionalization plays an important role in DE S-T .…”

“…7,12 DIAn (open-shell) has a y 0 of 0.62 at the PUHF, while the y 0 is only 0.21 at the CASCI. 16 Considering systems as biradicals in the ground state while the contribution of the biradical form in the ground state would be less than 50% appears somewhat strange. Therefore, nding a way to estimate the biradical character would constitute a breakthrough in the domain.…”

“…1 Several kinds of delocalized open-shell compounds that can be written with a Kekulé resonance form have been prepared based on aromatic six-membered rings as acenes longer than 6 rings, 2 anthenes, 3 peri-acenes, 4 rylene ribbons 5 and acenoacenes 6 or based on quinoidal compounds comprising only 6-membered rings (6-MR) as zethrene derivatives 7 or with the inclusion of two 7-membered rings (7-MRs) as heptalene derivatives 8 or 5membered rings in the p-conjugated core as bisphenalenyl derivatives 9 and diindeno-based PHs. [10][11][12][13][14][15][16] Among them, diindeno-based PHs are the most developed owing to their rather facile preparation at least for the small members. Since Kekuléan biradicaloid systems are resonance hybrids between the closed-and the open-shell forms, the contribution of each form in the ground state is described by the biradical character a UMR CNRS 8180, UVSQ, Institut Lavoisier de Versailles, Université Paris-Saclay, 45 avenue des Etats-Unis, 78035 Versailles Cedex, France.…”