We present a theoretical study on the structural and electronic properties of the p-dimethylamino-cinnamaldehyde (DMACA) merocyanine molecule in solvents of different polarities by combining the free energy gradient and the average solvent electrostatic configuration methods via an iterative procedure based on the sequential quantum mechanics/molecular mechanics hybrid methodology. Studying such a system in solution is a crucial step for understanding the solvent effects on its properties, which can have implications in fields such as optoelectronics and biophysics. We found that the DMACA molecule presents different geometries in nonpolar and polar solvents, changing from a polyene-like structure with a pyramidal dimethylamino group (in gas phase or nonpolar solvents) to a cyanine-like structure with a planar dimethylamino group in water due to the stabilizing effect of hydrogen bonds between DMACA and water. The molecular absorption spectrum showed a significant change, increasing solvent polarity with a large shift of the lower energy band, while the other two low lying bands did not shift significantly. The study accurately described the solvatochromic shift of the lowest-energy band and analyzed the structure of the excited states in terms of the one-electron transition density matrix, which showed that the dominant excited state (associated with the first lower energy band) is characterized by a local excitation on the benzene ring with charge transfer character to the carbon conjugated segment.

1.
I.
McMurrough
and
J.
McDowell
, “
Chromatographic separation and automated analysis of flavanols
,”
Anal. Biochem.
91
(
1
),
92
100
(
1978
).
2.
J. A.
Delcour
and
D. J.
de Varebeke
, “
A New Colourimetric Assay for Flavanoids in Pilsner Beers
,”
J. Inst. Brew.
91
(
1
),
37
40
(
1985
).
3.
D.
Treutter
, “
Chemical reaction detection of catechins and proanthocyanidins with 4-dimethylaminocinnamaldehyde
,”
J. Chromatogr. A
467
(
C
),
185
193
(
1989
).
4.
C. W.
Nagel
and
Y.
Glories
, “
Use of a modified dimethylaminocinnamaldehyde reagent for analysis of flavanols
,”
Am. J. Enol. Vitic.
42
(
4
),
364
366
(
1991
).
5.
W.
Feucht
,
D.
Treutter
, and
E.
Christ
, “
The precise localization of catechins and proanthocyanidins in protective layers around fungal infections/Über die exakte Lokalisierung von Catechinen und Proanthocyanidinen in Abgrenzungsgeweben um pilzliche Infektionen
,”
Z. Pflanzenkrankh. Pflanzenschutz/J. Plant Dis. Prot.
99
(
4
),
404
413
(
1992
).
6.
V. N.
Nesterov
,
T. v.
Timofeeva
,
M. Y.
Antipin
, and
R. D.
Clark
, “
A combinatorial chemistry approach to new materials for non-linear optics. II. 4-(Dimethylamino)cinnamaldehyde and a molecular complex of 4-methoxycinnamaldehyde with 2,4-dinitroaniline
,”
Acta Crystallogr., Sect. C
56
(
8
),
976
978
(
2000
).
7.
S.
Panja
and
S.
Chakravorti
, “
Photophysics of 4-(N,N-dimethylamino)cinnamaldehyde/α-cyclodextrin inclusion complex
,”
Spectrochim. Acta, Part A
58
(
1
),
113
122
(
2002
).
8.
P. R.
Bangal
,
S.
Panja
, and
S.
Chakravorti
, “
Excited state photodynamics of 4-N,N-dimethylamino cinnamaldehyde: A solvent dependent competition of TICT and intermolecular hydrogen bonding
,”
J. Photochem. Photobiol., A
139
(
1
),
5
16
(
2001
).
9.
S.
Panja
,
P.
Ranjan Bangal
, and
S.
Chakravorti
, “
Modulation of photophysics due to orientational selectivity of 4-N,N-dimethylamino cinnamaldehyde β-cyclodextrin inclusion complex in different solvents
,”
Chem. Phys. Lett.
329
(
5–6
),
377
385
(
2000
).
10.
K.
Coutinho
,
H. C.
Georg
,
T. L.
Fonseca
,
V.
Ludwig
, and
S.
Canuto
, “
An efficient statistically converged average configuration for solvent effects
,”
Chem. Phys. Lett.
437
(
1–3
),
148
152
(
2007
).
11.
I. F.
Galván
,
M. L.
Sánchez
,
M.
Martín
,
F. J.
Olivares del Valle
, and
M. A.
Aguilar
, “
ASEP/MD: A program for the calculation of solvent effects combining QM/MM methods and the mean field approximation
,”
Comput. Phys. Commun.
155
(
3
),
244
259
(
2003
).
12.
Y.
Orozco-Gonzalez
,
M.
Manathunga
,
M. D. C.
Marín
,
D.
Agathangelou
,
K. H.
Jung
,
F.
Melaccio
,
N.
Ferré
,
S.
Haacke
,
K.
Coutinho
,
S.
Canuto
, and
M.
Olivucci
, “
An average solvent electrostatic configuration protocol for QM/MM free energy optimization: Implementation and application to rhodopsin systems
,”
J. Chem. Theory Comput.
13
(
12
),
6391
6404
(
2017
).
13.
N. K.
Karmakar
,
S.
Pandey
,
R. K.
Pandey
, and
S. S.
Shukla
, “
Solvatochromism: A tool for solvent discretion for UV-Vis spectroscopic studies
,”
Appl. Spectrosc. Rev.
56
(
6
),
513
529
(
2021
).
14.
V.
Barone
,
R.
Improta
, and
N.
Rega
, “
Quantum mechanical computations and spectroscopy: From small rigid molecules in the gas phase to large flexible molecules in solution
,”
Acc. Chem. Res.
41
(
5
),
605
616
(
2008
).
15.
S.
Del Galdo
,
B.
Chandramouli
,
G.
Mancini
, and
V.
Barone
, “
Assessment of multi-scale approaches for computing UV–Vis spectra in condensed phases: Toward an effective yet reliable integration of variational and perturbative QM/MM approaches
,”
J. Chem. Theory Comput.
15
(
5
),
3170
3184
(
2019
).
16.
M. A.
Thompson
, “
QM/MMpol: A consistent model for solute/solvent polarization. Application to the aqueous solvation and spectroscopy of formaldehyde, acetaldehyde, and acetone
,”
J. Phys. Chem.
100
(
34
),
14492
14507
(
1996
).
17.
D.
Loco
,
L.
Lagardère
,
S.
Caprasecca
,
F.
Lipparini
,
B.
Mennucci
, and
J.-P.
Piquemal
, “
Hybrid QM/MM molecular dynamics with AMOEBA polarizable embedding
,”
J. Chem. Theory Comput.
13
(
9
),
4025
4033
(
2017
).
18.
T.
Giovannini
,
P.
Lafiosca
,
B.
Chandramouli
,
V.
Barone
, and
C.
Cappelli
, “
Effective yet reliable computation of hyperfine coupling constants in solution by a QM/MM approach: Interplay between electrostatics and non-electrostatic effects
,”
J. Chem. Phys.
150
(
12
),
124102
(
2019
).
19.
T.
Giovannini
and
C.
Cappelli
, “
Continuum vs. atomistic approaches to computational spectroscopy of solvated systems
,”
Chem. Commun.
59
(
38
),
5644
5660
(
2023
).
20.
G.
Colherinhas
,
L. B. A.
Oliveira
,
M. A.
Castro
,
T. L.
Fonseca
,
K.
Coutinho
, and
S.
Canuto
, “
On the calculation of magnetic properties of nucleic acids in liquid water with the sequential QM/MM method
,”
J. Mol. Liq.
294
,
111611
(
2019
).
21.
L. B.
Assis Oliveira
,
T.
L Fonseca
, and
B. J. C.
Cabral
, “
15N NMR shifts of eumelanin building blocks in water: A combined quantum mechanics/statistical mechanics approach
,”
Molecules
25
(
16
),
3616
(
2020
).
22.
M. H.
Cardenuto
,
H. M.
Cezar
,
K. V.
Mikkelsen
,
S. P. A.
Sauer
,
K.
Coutinho
, and
S.
Canuto
, “
A QM/MM study of the conformation stability and electronic structure of the photochromic switches derivatives of DHA/VHF in acetonitrile solution
,”
Spectrochim. Acta, Part A
251
,
119434
(
2021
).
23.
H. M.
Cezar
,
S.
Canuto
, and
K.
Coutinho
, “
Understanding the absorption spectrum of mesityl oxide dye in solvents of different polarities
,”
J. Mol. Liq.
307
,
112924
(
2020
).
24.
J. L.
Silva
,
I.
Unger
,
T. A.
Matias
,
L. R.
Franco
,
G.
Damas
,
L. T.
Costa
,
K. C. F.
Toledo
,
T. C. R.
Rocha
,
A. N.
de Brito
,
C. M.
Saak
,
K.
Coutinho
,
K.
Araki
,
O.
Björneholm
,
B.
Brena
, and
C. M.
Araujo
, “
X-ray photoelectron fingerprints of high-valence ruthenium-oxo complexes along the oxidation reaction pathway in an aqueous environment
,”
J. Phys. Chem. Lett.
10
(
24
),
7636
7643
(
2019
).
25.
K.
Coutinho
and
S.
Canuto
, “
The sequential Monte Carlo-quantum mechanics methodology. Application to the solvent effects in the Stokes shift of acetone in water
,”
J. Mol. Struct.: THEOCHEM
632
(
1–3
),
235
246
(
2003
).
26.
S.
Canuto
and
K.
Coutinho
, “
From hydrogen bond to bulk: Solvation analysis of the n-π* transition of formaldehyde in water
,”
Int. J. Quantum Chem.
77
(
1
),
192
198
(
2000
).
27.
K.
Coutinho
and
S.
Canuto
, “
Solvent effects in emission spectroscopy: A Monte Carlo quantum mechanics study of the n ← π* shift of formaldehyde in water
,”
J. Chem. Phys.
113
(
20
),
9132
9139
(
2000
).
28.
K.
Coutinho
,
S.
Canuto
, and
M. C.
Zerner
, “
A Monte Carlo-quantum mechanics study of the solvatochromic shifts of the lowest transition of benzene
,”
J. Chem. Phys.
112
(
22
),
9874
9880
(
2000
).
29.
Y.
Kitamura
,
N.
Takenaka
,
Y.
Koyano
, and
M.
Nagaoka
,
Challenges and Advances in Computational Chemistry and Physics
(
Springer
,
2015
), pp.
219
252
.
30.
N.
Okuyama-Yoshida
,
M.
Nagaoka
, and
T.
Yamabe
, “
Transition-state optimization on free energy surface: Toward solution chemical reaction ergodography
,”
Int. J. Quantum Chem.
70
(
1
),
95
103
(
1998
).
31.
H. C.
Georg
,
T. S.
Fernandes
,
S.
Canuto
,
N.
Takenaka
,
Y.
Kitamura
, and
M.
Nagaoka
,
Practical Aspects of Computational Chemistry III
(
Springer
,
2014
), pp.
231
247
.
32.
H. C.
Georg
and
S.
Canuto
, “
Electronic properties of water in liquid environment. A sequential QM/MM study using the free energy gradient method
,”
J. Phys. Chem. B
116
(
36
),
11247
11254
(
2012
).
33.
E. M.
Torres
,
H. C.
Georg
,
T. L.
Fonseca
, and
M. A.
Castro
, “
First hyperpolarizability of isomers of pyridinium N-phenoxide betaine dye in solution using the ASEC-FEG method
,”
Chem. Phys. Lett.
699
,
261
266
(
2018
).
34.
V.
Ludwig
,
Z. M.
da Costa Ludwig
,
D.
Valverde
,
H.
Georg
, and
S.
Canuto
, “
Free energy gradient for understanding the stability and properties of neutral and charged L-alanine molecule in water
,”
J. Mol. Liq.
319
,
114109
(
2020
).
35.
I.
Brandão
,
T. L.
Fonseca
,
H. C.
Georg
,
M. A.
Castro
, and
R. B.
Pontes
, “
Assessing the structure and first hyperpolarizability of Li@B10H14 in solution: A sequential QM/MM study using the ASEC–FEG method
,”
Phys. Chem. Chem. Phys.
22
(
30
),
17314
17324
(
2020
).
36.
D.
Valverde
,
A.
Vasconcelos Sanches De Araujo
,
A.
Carlos Borin
, and
S.
Canuto
, “
Electronic structure and absorption spectra of fluorescent nucleoside analogues
,”
Phys. Chem. Chem. Phys.
19
(
43
),
29354
29363
(
2017
).
37.
I.
Brandão
,
T. L.
Fonseca
,
L. R.
Franco
,
H. C.
Georg
, and
M. A.
Castro
, “
Applicability of DFT functionals for evaluating the first hyperpolarizability of phenol blue in solution
,”
J. Chem. Phys.
154
(
9
),
094501
(
2021
).
38.
I.
Brandão
,
L. R.
Franco
,
T. L.
Fonseca
,
M. A.
Castro
, and
H. C.
Georg
, “
Confirming the relationship between first hyperpolarizability and the bond length alternation coordinate for merocyanine dyes
,”
J. Chem. Phys.
146
(
22
),
224505
(
2017
).
39.
L. R.
Franco
,
I.
Brandão
,
T. L.
Fonseca
, and
H. C.
Georg
, “
Elucidating the structure of merocyanine dyes with the ASEC-FEG method. Phenol blue in solution
,”
J. Chem. Phys.
145
(
19
),
194301
(
2016
).
40.
W. L.
Jorgensen
,
D. S.
Maxwell
, and
J.
Tirado-Rives
, “
Development and testing of the OPLS all-atom force field on conformational energetics and properties of organic liquids
,”
J. Am. Chem. Soc.
118
(
45
),
11225
11236
(
1996
).
41.
B. H.
Besler
,
K. M.
Merz
, and
P. A.
Kollman
, “
Atomic charges derived from semiempirical methods
,”
J. Comput. Chem.
11
(
4
),
431
439
(
1990
).
42.
G.
Kaminski
,
E. M.
Duffy
,
T.
Matsui
, and
W. L.
Jorgensen
, “
Free energies of hydration and pure liquid properties of hydrocarbons from the OPLS all-atom model
,”
J. Phys. Chem.
98
(
49
),
13077
13082
(
1994
).
43.
H. J.
Böhm
,
I. R.
McDonald
, and
P. A.
Madden
, “
An effective pair potential for liquid acetonitrile
,”
Mol. Phys.
49
(
2
),
347
360
(
1983
).
44.
H. J. C.
Berendsen
,
J. R.
Grigera
, and
T. P.
Straatsma
, “
The missing term in effective pair potentials
,”
J. Phys. Chem.
91
(
24
),
6269
6271
(
1987
).
45.
K.
Coutinho
,
M. J.
De Oliveira
, and
S.
Canuto
, “
Sampling configurations in Monte Carlo simulations for quantum mechanical studies of solvent effects
,”
Int. J. Quantum Chem.
66
(
3
),
249
253
(
1998
).
46.
H. M.
Cezar
,
S.
Canuto
, and
K.
Coutinho
, “
DICE: A Monte Carlo code for molecular simulation including the configurational bias Monte Carlo method
,”
J. Chem. Inf. Model.
60
(
7
),
3472
3488
(
2020
).
47.
D. J. F. M. J.
Frisch
,
G. W.
Trucks
,
H. B.
Schlegel
,
G. E.
Scuseria
,
M. A.
Robb
,
J. R.
Cheeseman
,
G.
Scalmani
,
V.
Barone
,
B.
Mennucci
,
G. A.
Petersson
,
H.
Nakatsuji
,
M.
Caricato
,
X.
Li
,
H. P.
Hratchian
,
A. F.
Izmaylov
,
J.
Bloino
,
G.
Zheng
,
J. L.
Sonnenberg
,
M.
Had
,
M. J.
Frisch
,
G. W.
Trucks
,
H. B.
Schlegel
,
G. E.
Scuseria
,
M. A.
Robb
,
J. R.
Cheeseman
,
G.
Scalmani
,
V.
Barone
,
B.
Mennucci
,
G. A.
Petersson
,
H.
Nakatsuji
,
M.
Caricato
,
X.
Li
,
H. P.
Hratchian
,
A. F.
Izmaylov
,
J.
Bloino
,
G.
Zheng
,
J. L.
Sonnenberg
,
M.
Hada
,
M.
Ehara
,
K.
Toyota
,
R.
Fukuda
,
J.
Hasegawa
,
M.
Ishida
,
T.
Nakajima
,
Y.
Honda
,
O.
Kitao
,
H.
Nakai
,
T.
Vreven
,
J. A.
Montgomery
, Jr.
,
J. E.
Peralta
,
F.
Ogliaro
,
M.
Bearpark
,
J. J.
Heyd
,
E.
Brothers
,
K. N.
Kudin
,
V. N.
Staroverov
,
R.
Kobayashi
,
J.
Normand
,
K.
Raghavachari
,
A.
Rendell
,
J. C.
Burant
,
S. S.
Iyengar
,
J.
Tomasi
,
M.
Cossi
,
N.
Rega
,
J. M.
Millam
,
M.
Klene
,
J. E.
Knox
,
J. B.
Cross
,
V.
Bakken
,
C.
Adamo
,
J.
Jaramillo
,
R.
Gomperts
,
R. E.
Stratmann
,
O.
Yazyev
,
A. J.
Austin
,
R.
Cammi
,
C.
Pomelli
,
J. W.
Ochterski
,
R. L.
Martin
,
K.
Morokuma
,
V. G.
Zakrzewski
,
G. A.
Voth
,
P.
Salvador
,
J. J.
Dannenberg
,
S.
Dapprich
,
A. D.
Daniels
,
Ö.
Farkas
,
J. B.
Foresman
,
J.
V Ortiz
,
J.
Cioslowski
, and
D. J.
Fox
,
GAUSSIAN 09, Revision D.01
,
Gaussian Inc.
,
Wallingford, Wallingford CT
,
2013
.
48.
H. C.
Georg
and
S.
Canuto
, DICEPLAYER: An interface between Dice and Gaussian programs,
2013
.
49.
R. H.
Baughman
,
B. E.
Kohler
,
I. J.
Levy
, and
C.
Spangler
, “
The crystal structure of trans,trans-1,3,5,7-octatetraene as a model for fully-ordered trans-polyacetylene
,”
Synth. Met.
11
(
1
),
37
52
(
1985
).
50.
W.
Drenth
and
E. H.
Wiebenga
, “
Structure of α,ω-diphenyl-polyenes. IV. Crystal and molecular structure of 1,8-diphenyl-1,3,5,7-octatetraene
,”
Acta Crystallogr.
8
(
12
),
755
760
(
1955
).
51.
F.
Plasser
and
H.
Lischka
, “
Analysis of excitonic and charge transfer interactions from quantum chemical calculations
,”
J. Chem. Theory Comput.
8
(
8
),
2777
2789
(
2012
).
52.
F.
Plasser
, “
TheoDORE: A toolbox for a detailed and automated analysis of electronic excited state computations
,”
J. Chem. Phys.
152
(
8
),
084108
(
2020
).
53.
S.
Mai
,
F.
Plasser
,
J.
Dorn
,
M.
Fumanal
,
C.
Daniel
, and
L.
Gonzalez
, “
Quantitative wave function analysis for excited states of transition metal complexes
,”
Coord. Chem. Rev.
361
,
74
97
(
2018
).
54.
P.
Kimber
and
F.
Plasser
, “
Toward an understanding of electronic excitation energies beyond the molecular orbital picture
,”
Phys. Chem. Chem. Phys.
22
(
11
),
6058
6080
(
2020
).

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