TY - JOUR

T1 - Dual emission of 2-amino-4-methylpyrimidine

T2 - A theoretical study

AU - Shekhovtsov, N. A.

AU - Vinogradova, K. A.

AU - Nikolaenkova, E. B.

AU - Krivopalov, V. P.

AU - Bushuev, M. B.

N1 - Publisher Copyright: © 2020, Pleiades Publishing, Ltd. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2020/10

Y1 - 2020/10

N2 - Abstract: DFT and TD-DFT calculations at the B3LYP/LANL2DZ level of theory are performed in order to explain the origins of dual fluorescence and uncover the relaxation pathways of 2-amino-4-methylpyrimidine (L). The computations are in good agreement with experimental data. A high-energy emission band in the photoluminescence spectrum of 2-amino-4-methylpyrimidine (λ max = 350 nm) is related to the fluorescence of monomer L. Comparison of calculated and experimental IR and absorption spectra reveals that in the solid state L molecules form supramolecular {N–H···N} n hydrogen bonded associates. The formation of such associates favors the excited state double proton transfer (ESDPT). Calculated 2D potential energy curves for the ground and first singlet excited states of dimeric associates L 2 indicate the presence of two stable forms, L 2-amino and L 2-imino. The low-energy band in the emission spectrum of 2-amino-4-methylpyrimidine (λ max = 445 nm) is probably associated with the fluorescence of the L 2-imino form. Both fluorescence bands have a mixed π–π*, n–π* character as is evidenced by frontier orbitals involved in S 1–S 0 transitions.

AB - Abstract: DFT and TD-DFT calculations at the B3LYP/LANL2DZ level of theory are performed in order to explain the origins of dual fluorescence and uncover the relaxation pathways of 2-amino-4-methylpyrimidine (L). The computations are in good agreement with experimental data. A high-energy emission band in the photoluminescence spectrum of 2-amino-4-methylpyrimidine (λ max = 350 nm) is related to the fluorescence of monomer L. Comparison of calculated and experimental IR and absorption spectra reveals that in the solid state L molecules form supramolecular {N–H···N} n hydrogen bonded associates. The formation of such associates favors the excited state double proton transfer (ESDPT). Calculated 2D potential energy curves for the ground and first singlet excited states of dimeric associates L 2 indicate the presence of two stable forms, L 2-amino and L 2-imino. The low-energy band in the emission spectrum of 2-amino-4-methylpyrimidine (λ max = 445 nm) is probably associated with the fluorescence of the L 2-imino form. Both fluorescence bands have a mixed π–π*, n–π* character as is evidenced by frontier orbitals involved in S 1–S 0 transitions.

KW - dual emission

KW - pyrimidine

KW - hydrogen bond

KW - photoisomerization

KW - excited state double proton transfer

KW - supramolecular chemistry

KW - DOUBLE-PROTON-TRANSFER

KW - CRYSTAL-STRUCTURE

KW - COMPLEX

KW - DFT

UR - http://www.scopus.com/inward/record.url?scp=85106854873&partnerID=8YFLogxK

U2 - 10.1134/S0022476620100042

DO - 10.1134/S0022476620100042

M3 - Article

VL - 61

SP - 1521

EP - 1529

JO - Journal of Structural Chemistry

JF - Journal of Structural Chemistry

SN - 0022-4766

IS - 10

ER -