Regioisomeric engineering of carbazole-naphthalimide donor-acceptor systems enables efficient triplet generation and room temperature phosphorescence in molecular and nanoaggregated states.
- 1Department of Chemistry, Biology and Biotechnology, University of Perugia via Elce di Sotto No. 8 06123 Perugia Italy [email protected].
- 2Organic Materials Laboratory, Department of Chemistry, Indian Institute of Technology Roorkee Roorkee 247667 India [email protected].
Abstract
Regioisomeric engineering provides an effective strategy for controlling excited-state dynamics in donor-acceptor systems, yet its influence on triplet generation and room-temperature phosphorescence (RTP) remains insufficiently understood. Herein, we report two series of carbazole-phenyl-naphthalimide donor-acceptor regioisomers in which carbazole is connected to either the C3 or C4 position of the naphthalimide acceptor through ortho-, meta-, and para-substituted phenyl linkers. Systematic photophysical investigations reveal that subtle changes in molecular connectivity profoundly influence charge-transfer character, fluorescence and intersystem crossing efficiency. Para-linked and C4-substituted derivatives exhibit enhanced fluorescence owing to improved conjugation and reduced structural relaxation, whereas ortho- and meta-isomers as well as C3-substitution promote more efficient triplet generation through spin-orbit charge-transfer-assisted intersystem crossing, yielding triplet quantum yields approaching unity. Femtosecond and nanosecond transient absorption spectroscopy directly elucidate the singlet-to-triplet conversion dynamics, while TD-DFT calculations and single-crystal X-ray diffraction establish clear relationships between molecular geometry, electronic coupling, and excited-state behaviour. Efficient orange-to-red RTP is observed in benzophenone host-guest matrices as well as in water-dispersed nanoaggregates, suggesting that regioisomeric control can activate persistent phosphorescence in both solid-state and colloidal environments. These findings provide valuable molecular design principles for developing purely organic RTP materials for optoelectronics, time-resolved bioimaging, and photonic applications.
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BibTeX
@article{mancini2026regioisomeric,
title = {{Regioisomeric engineering of carbazole-naphthalimide donor-acceptor systems enables efficient triplet generation and room temperature phosphorescence in molecular and nanoaggregated states.}},
author = {Pietro Mancini and Siddan Gouthaman and Vignesh Rajendran and Chiara Montanari and Valentina Titone and K R Justin Thomas and Benedetta Carlotti},
journal = {Chemical science},
year = {2026},
month = oct,
doi = {10.1039/d6sc06161c},
url = {https://europepmc.org/article/MED/42899001},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - Regioisomeric engineering of carbazole-naphthalimide donor-acceptor systems enables efficient triplet generation and room temperature phosphorescence in molecular and nanoaggregated states.
AU - Pietro Mancini
AU - Siddan Gouthaman
AU - Vignesh Rajendran
AU - Chiara Montanari
AU - Valentina Titone
AU - K R Justin Thomas
AU - Benedetta Carlotti
PY - 2026
DA - 2026/10/14
JO - Chemical science
DO - 10.1039/d6sc06161c
UR - https://europepmc.org/article/MED/42899001
AB - Regioisomeric engineering provides an effective strategy for controlling excited-state dynamics in donor-acceptor systems, yet its influence on triplet generation and room-temperature phosphorescence (RTP) remains insufficiently understood. Herein, we report two series of carbazole-phenyl-naphthalimide donor-acceptor regioisomers in which carbazole is connected to either the C3 or C4 position of the naphthalimide acceptor through ortho-, meta-, and para-substituted phenyl linkers. Systematic photophysical investigations reveal that subtle changes in molecular connectivity profoundly influence charge-transfer character, fluorescence and intersystem crossing efficiency. Para-linked and C4-substituted derivatives exhibit enhanced fluorescence owing to improved conjugation and reduced structural relaxation, whereas ortho- and meta-isomers as well as C3-substitution promote more efficient triplet generation through spin-orbit charge-transfer-assisted intersystem crossing, yielding triplet quantum yields approaching unity. Femtosecond and nanosecond transient absorption spectroscopy directly elucidate the singlet-to-triplet conversion dynamics, while TD-DFT calculations and single-crystal X-ray diffraction establish clear relationships between molecular geometry, electronic coupling, and excited-state behaviour. Efficient orange-to-red RTP is observed in benzophenone host-guest matrices as well as in water-dispersed nanoaggregates, suggesting that regioisomeric control can activate persistent phosphorescence in both solid-state and colloidal environments. These findings provide valuable molecular design principles for developing purely organic RTP materials for optoelectronics, time-resolved bioimaging, and photonic applications.
SN - 2041-6520
SN - 2041-6539
ER -