Influence of the number and substitution position of phenyl groups on the aggregation-enhanced emission of benzene-cored luminogens

Abstract

The influence of the number and substitution position of phenyl groups on the aggregation-enhanced emission of benzene-cored luminogens is unambiguously revealed.

Persistent Solid‐State Phosphorescence and Delayed Fluorescence at Room Temperature by a Twisted Hydrocarbon

“…This faint persistent RTPcan be linked to SOC induced by the twisting of the outer rings, since crystalline 6 adopts anon-planar dissymmetric structure where one phenyl substituent tilts out of the central benzene plane in the opposite direction to the other two phenyls,with dihedral angles of + 35.18 8, À34.58 8,a nd À38.48 8 at the single bonds. [22] In contrast to the rare reports of persistent RTP from hydrocarbons in the solid state in ambient atmosphere, DF from pure hydrocarbons at room temperature has only been observed under exclusion of oxygen, originating from surface sites. [23] Introducing saturated bridges between the benzene rings of 6 is am eans of rigidifying the angle between benzenes at af ixed value,h indering rotational pathways of triplet deactivation without fundamental changes to the chromophore that would result from unsaturated bridges.T ruxene 7, the symmetrically triply methylene-bridged derivative of 6,is obtained by acid-catalyzed trimerizing cyclodehydration of 1indanone, [24] similar to the synthesis of 6 from acetophenone.…”

“…[12] Innovative approaches for the improvement of RTPv ia intermolecular interactions are crystallization-induced phosphorescence, [9] halogen bonding in co-crystals, [13] aggregation-induced ISC, [14] complexationinduced RTPi ns olution, [15] and emission from H-aggregates. [22] In contrast to the rare reports of persistent RTP Scheme 1. However,ahydrocarbon whose persistent solid-state RTP was noted early is tetraphenylmethane 4.…”

“…[16] In general, electronic transitions between non-coplanar (orthogonal or tilted) orbitals are necessary to allow for spinorbit coupling (SOC), [17,18] but the vast majority of polycyclic aromatic compounds do not present this kind of geometry. [22] In contrast to the rare reports of persistent RTP Scheme 1. [19] Its peculiar threedimensional structure of four-fold symmetry [20] distinguishes 4 from most polycyclic arenes,w hich generally show no persistent RTPi nt he pure crystalline state.V ery weak longlived RTPint he crystal has also been reported [3] forthe two C 3 -symmetric species triphenylene 5 [21] and sym-triphenylbenzene 6 (which is non-planar).…”

“…However,ahydrocarbon whose persistent solid-state RTP was noted early is tetraphenylmethane 4. [22] In contrast to the rare reports of persistent RTP Scheme 1. This faint persistent RTPcan be linked to SOC induced by the twisting of the outer rings, since crystalline 6 adopts anon-planar dissymmetric structure where one phenyl substituent tilts out of the central benzene plane in the opposite direction to the other two phenyls,with dihedral angles of + 35.18 8, À34.58 8,a nd À38.48 8 at the single bonds.…”

“…This faint persistent RTPcan be linked to SOC induced by the twisting of the outer rings, since crystalline 6 adopts anon-planar dissymmetric structure where one phenyl substituent tilts out of the central benzene plane in the opposite direction to the other two phenyls,with dihedral angles of + 35.18 8, À34.58 8,a nd À38.48 8 at the single bonds. [22] In contrast to the rare reports of persistent RTP Scheme 1. Exemplary metal-free materials whose crystals show RTP.Scheme 2.…”