TY - JOUR

T1 - Computational investigation of substituent effects on the fluorescence wavelengths of oxyluciferin analogs

AU - Satalkar, Vardhan

AU - Benassi, Enrico

AU - Mao, Yuezhi

AU - Pan, Xiaoliang

AU - Ran, Chongzhao

AU - Chen, Xiaoyuan

AU - Shao, Yihan

N1 - Funding Information: We thank Drs. Yajun Liu, Peng Tao, Zheng Pei, and Shushu Zhang for helpful discussions. YS was supported by the National Institutes of Health, USA (grant No. R01GM135392) and the Office of the Vice President of Research and the College of Art and Sciences at the University of Oklahoma (OU). EB expresses his gratitude to NSU and 5–100 Excellence Programme of Russian Ministry of Science and Education. The authors thank the OU Supercomputing Center for Education & Research (OSCER) for the computational resources. Publisher Copyright: © 2022 Elsevier B.V.

PY - 2022/10/1

Y1 - 2022/10/1

N2 - Oxyluciferin, which is the light emitter for firefly bioluminescence, has been subjected to extensive chemical modifications to tune its emission wavelength and quantum yield. However, the exact mechanisms for various electron-donating and withdrawing groups to perturb the photophysical properties of oxyluciferin analogs are still not fully understood. To elucidate the substituent effects on the fluorescence wavelength of oxyluciferin analogs, we applied the absolutely localized molecular orbitals (ALMO)-based frontier orbital analysis to assess various types of interactions (i.e. permanent electrostatics/exchange repulsion, polarization, occupied–occupied orbital mixing, virtual–virtual orbital mixing, and charge-transfer) between the oxyluciferin and substituent orbitals. We suggested two distinct mechanisms that can lead to red-shifted oxyluciferin emission wavelength, a design objective that can help increase the tissue penetration of bioluminescence emission. Within the first mechanism, an electron-donating group (such as an amino or dimethylamino group) can contribute its highest occupied molecular orbital (HOMO) to an out-of-phase combination with oxyluciferin's HOMO, thus raising the HOMO energy of the substituted analog and narrowing its HOMO-LUMO gap. Alternatively, an electron-withdrawing group (such as a nitro or cyano group) can participate in an in-phase virtual–virtual orbital mixing of fragment LUMOs, thus lowering the LUMO energy of the substituted analog. Such an ALMO-based frontier orbital analysis is expected to lead to intuitive principles for designing analogs of not only the oxyluciferin molecule, but also many other functional dyes.

AB - Oxyluciferin, which is the light emitter for firefly bioluminescence, has been subjected to extensive chemical modifications to tune its emission wavelength and quantum yield. However, the exact mechanisms for various electron-donating and withdrawing groups to perturb the photophysical properties of oxyluciferin analogs are still not fully understood. To elucidate the substituent effects on the fluorescence wavelength of oxyluciferin analogs, we applied the absolutely localized molecular orbitals (ALMO)-based frontier orbital analysis to assess various types of interactions (i.e. permanent electrostatics/exchange repulsion, polarization, occupied–occupied orbital mixing, virtual–virtual orbital mixing, and charge-transfer) between the oxyluciferin and substituent orbitals. We suggested two distinct mechanisms that can lead to red-shifted oxyluciferin emission wavelength, a design objective that can help increase the tissue penetration of bioluminescence emission. Within the first mechanism, an electron-donating group (such as an amino or dimethylamino group) can contribute its highest occupied molecular orbital (HOMO) to an out-of-phase combination with oxyluciferin's HOMO, thus raising the HOMO energy of the substituted analog and narrowing its HOMO-LUMO gap. Alternatively, an electron-withdrawing group (such as a nitro or cyano group) can participate in an in-phase virtual–virtual orbital mixing of fragment LUMOs, thus lowering the LUMO energy of the substituted analog. Such an ALMO-based frontier orbital analysis is expected to lead to intuitive principles for designing analogs of not only the oxyluciferin molecule, but also many other functional dyes.

KW - Bioluminescence

KW - Energy decomposition analysis

KW - Fluorescence

KW - Substitution

KW - Time-dependent density functional theory

UR - http://www.scopus.com/inward/record.url?scp=85130523783&partnerID=8YFLogxK

U2 - 10.1016/j.jphotochem.2022.114018

DO - 10.1016/j.jphotochem.2022.114018

M3 - Article

C2 - 36407037

AN - SCOPUS:85130523783

VL - 431

JO - Journal of Photochemistry and Photobiology A: Chemistry

JF - Journal of Photochemistry and Photobiology A: Chemistry

SN - 1010-6030

M1 - 114018

ER -