Biluminescence via Fluorescence and Persistent Phosphorescence in Amorphous Organic Donor(D₄)–Acceptor(A) Conjugates and Application in Data Security Protection

Abstract

Purely organic biluminescent materials are of great interest due to the involvement of both singlet and long-lived triplet emissions, which have been rarely reported in bioimaging and organic light-emitting diodes. We show two molecules 3,4,5,6-tetraphenyloxy-phthalonitrile (POP) and 3,4,5,6-tetrakis- p-tolyloxy-phthalonitrile (TOP), in which POP was found to exhibit fluorescence and persistent room-temperature green phosphorescence (pRTGP) in the amorphous powder and crystal states. Both POP and TOP show aggregation-induced emission in a tetrahydrofuran-water mixture. We found in single-crystal X-ray analysis that intra- and intermolecular lp(O)···π interactions along with π(C = C)···π(C≡N), hydrogen bond (H-B), and C-H···π interactions induce a head-to-tail slipped-stack arrangement in POP. In addition, the X-ray structure of TOP with a slipped-stack arrangement induced by only π(C═C)···π(C≡N) and H-B interactions shows dim afterglow only in crystals. These indicate that more noncovalent interactions found in POP may reinforce relatively efficient intersystem crossing that leads to pRTGP. Given the unique green afterglow feature in amorphous powder of POP, document security protection application is achievable.

Asymmetric-donor (D2D2′)–acceptor (A) conjugates for simultaneously accessing intrinsic blue-RTP and blue-TADF

“…The compounds were synthesized via the traditional nucleophilic aromatic substitution reaction (S N R) between the phenol derivatives and 3,4,5,6-tetrafluorophthalonitrile. 30,31 The isolated intermediates were reacted separately with the sodium salt of carbazole to obtain the final compounds (CPPN, CPPNF) ( Fig. 2).…”

“…An alternative approach to substitute such systems with cheaper organic materials which can be easily processed and functionalized using a wide variety of substituents, is therefore desirable. Recently, purely organic RTP materials [23][24][25][26][27][28][29] have boosted tremendous interest in data security protection 30 and invisible ink, 31 and photodynamic therapy. 29 However, these systems show weak RTP due to inefficient ISC between the S 1 and T 1 states caused by the low SOC of the lighter elements present in the dye.…”

“…To observe both blue-TADF (BTADF) and blue-RTP (BRTP) simultaneously with high PLQY from the SCOLMs under ambient conditions becomes a difficult task in the field of chemical physics. To harvest triplet excitons simultaneously from a single molecule, fine-tuning of the singlet-triplet energy gap is required for both TADF and RTP, while intra-and/or intermolecular interactions (lpÁ Á Áp, pÁ Á Áp, hydrogen bonding) 27,30 and heavy elements are the prerequisites for RTP. 19 Recently, several design principles have been used to observe both TADF and RTP.…”

“…Hence, the development of such SCOLMs is of prime importance. Taking a cue from our previous reports of D 4 -A molecular systems 30,31 where the phenoxy or substituted phenoxy donors are covalently attached to either the phthalonitrile (PN) or the terephthalonitrile ring, here we attached both phenoxy or 2,5-difluorophenoxy and carbazole donors at the 4,5 and 3,6-positions of the PN core respectively, to get mixed donor-acceptor (D 2 D 2 0 -A) geometries (CPPN, CPPNF) ( Fig. 2).…”

Modulation of Thermally Activated Delayed Fluorescence in Waterborne Polyurethanes via Charge‐Transfer Effect

“…In the past decades, purely organicl uminescentm aterials have experienced ab ooming development due to their enormous applicationsi nc hemical sensors, [1][2][3][4] optoelectronics, [5][6][7][8][9] bioimaging [10][11][12][13][14][15] and data storage. [16][17][18][19][20][21] Especially,t hermally activated delayed fluorescence( TADF), [22][23][24][25][26] discovered as the second band of long-lived emission, shows identical contour with the prompt fluorescence( PF) and has been widely used in organic light-emitting diodes (OLEDs). Indeed,T ADF,a lso known as E-type delayedf luorescence, [27] was first reported in 1961.…”