Structure and properties of N-heterocycle-containing benzotriazoles as UV absorbers

Article abstract of DOI:10.1016/j.molstruc.2013.09.045

Two N-heterocycle-containing benzotriazole compounds (CBHDCP, CBMPP) were synthesized and their structures were confirmed by FT-IR, ¹H NMR, mass spectroscopy and elemental analysis. Their spectral properties compared with that of a common commercial benzotriazole UV absorber Tinuvin 326 in solvents were measured and analyzed using molecular orbital calculations. It was found that the experimentally obtained optical properties were in close agreement with the theoretically obtained results. Besides, CBMPP is much superior to CBHDCP acting as an effective UV absorber on polyethylene terephthalate fabric due to its combinative higher exhaustion and higher molar extinction coefficient. The exhaustion difference on polyethylene terephthalate fabric among N-heterocycle-containing benzotriazoles (CBHDCP, CBMPP) and Tinuvin 326 were then measured and explained by the solubility parameter theory. The results agreed with the rule that compounds with higher exhaustion on fiber have solubility parameter much closer to that of fiber polymer.

Full text of DOI:10.1016/j.molstruc.2013.09.045

Journal of Molecular Structure 1054–1055 (2013) 94–99
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structure and properties of N-heterocycle-containing benzotriazoles
as UV absorbers
a,b
Zhihua Cui a,b, Xin Li b, Xidong Wang b, Kemei Pei a,c, , Weiguo Chen
⇑
a Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education of China, Zhejiang Sci-Tech University, Hangzhou 310018, China
b Engineering Research Center for Eco-Dyeing & Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, China
c Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
Two novel N-heterocycle-bearing UVAs were synthesized.
The excellent absorption comes from S0 ? S1 electronic transition band of the Enol forms.
CBHDCP and CBMPP show much higher emax than commercial UVA Tinuvin 326.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 July 2013
Received in revised form 20 September 2013
Accepted 23 September 2013
Available online 1 October 2013
Two N-heterocycle-containing benzotriazole compounds (CBHDCP, CBMPP) were synthesized and their
structures were confirmed by FT-IR, 1H NMR, mass spectroscopy and elemental analysis. Their spectral
properties compared with that of a common commercial benzotriazole UV absorber Tinuvin 326 in sol-
vents were measured and analyzed using molecular orbital calculations. It was found that the experimen-
tally obtained optical properties were in close agreement with the theoretically obtained results. Besides,
CBMPP is much superior to CBHDCP acting as an effective UV absorber on polyethylene terephthalate
fabric due to its combinative higher exhaustion and higher molar extinction coefficient. The exhaustion
difference on polyethylene terephthalate fabric among N-heterocycle-containing benzotriazoles
(CBHDCP, CBMPP) and Tinuvin 326 were then measured and explained by the solubility parameter the-
ory. The results agreed with the rule that compounds with higher exhaustion on fiber have solubility
parameter much closer to that of fiber polymer.
Keywords:
Benzotriazole
UV absorber
UV–visible spectroscopy
Molecular orbital calculations
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
wavelength region of 300–360 nm and hardly absorbing visible
light. The photostabilization mechanism of these type of com-
It is widely recognized that ultraviolet rays (UVR) in sunlight
(wavelengths between 280 nm and 400 nm) is an important factor
causing skin aging, eye disease [1] and photodegradation to some
organic substances such as polymers and colorants [2,3]. With the
ozone depletion in recent years, much more UVR has been progres-
sively reached the earth surface [4] and causes severe photo-in-
duced loss to organic materials. In order to protect against the
damaging effects of UVR on organic materials, addition of UV absor-
ber (UVA) is an effective and convenient solution in practice [5,6].
An ideal UVA must have the key property: highly efficient
absorption between 280 and 400 nm coupled with high optical
transparency in the visible range. 2-(2-Hydroxyphenyl)-benzotria-
zole derivatives are one sort of efficient UVA absorbing in the
pounds is based on the formation of intramolecular hydrogen
bonds (IMHB) between the o-hydroxyl group of the phenyl ring
and the nitrogen atom of the benzotriazole moiety and the excited
state intramolecular proton transfer (ESIPT) mechanism by
Oꢁ ꢁ ꢁHꢁ ꢁ ꢁN tunneling (Fig. 1) [7].
Since the discovery of 2-(2-hydroxyphenyl)-benzotriazole as a
UVA chromophore, most efforts have been focused on the effect
of substituent variation in benzotriazole chromophore [8,9] than
chromophore variation itself. In view of the introduction of hetero-
cycle to chromophore bringing lots of interesting properties, in this
work, heterocycle moiety was introduced to benzotriazole chro-
mophore and two novel N-heterocycle-containing benzotriazole
compounds (CBHDCP, CBMPP) were designed. The calculation re-
sults predicted they had much higher molar extinction coefficients
than that of Tinuvin 326, a common commercial benzotriazole
UVA. Then CBHDCP and CBMPP were synthesized from reactant
4-chloro-2-nitroaniline via diazotization, azo coupling, reductive
cyclization, acidification (Scheme 1) and characterized by FT-IR,
⇑
Corresponding author at: Key Laboratory of Advanced Textile Materials and
Manufacturing Technology, Ministry of Education of China, Zhejiang Sci-Tech
University, Hangzhou 310018, China. Tel.: +86 571 86843627.
E-mail address: xiaopei027@sina.com (K. Pei).
0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2013.09.045

Z. Cui et al. / Journal of Molecular Structure 1054–1055 (2013) 94–99
95
Cl
Cl
3. Experimental
3.1. Materials, equipment and analysis
hv
N
N
N
N
H
O
N
N
H
OH
The reagents, 4-chloro-2-nitroaniline, sodium nitrite, N-methyl-
3-cyano-6-hydroxy-4-methyl-2-pyridone and 1-phenyl-3-methyl-
5-pyrazolone, concentrated hydrochloric acid, thiourea dioxide,
sodium carbonate, sodium hydroxide and the dispersant sodium
methylenedinaphthalene disulphonate (NNO) were bought from
Aladdin Reagent Co. Ltd (Shanghai, China). Tinuvin 326 was bought
from Shinyang Chemical Co. Ltd (Hangzhou, China).
Ground state
Excited state
Fig. 1. The excited state intramolecular proton transfer (ESIPT) mechanism of
Tinuvin 326.
1H NMR, mass spectroscopy as well as elemental analysis. Quan-
tum chemistry calculations were carried out to investigate the sta-
ble structure and UV electronic absorption bands of CBHDCP,
CBMPP and Tinuvin 326.
The prepared CBHDCP and CBMPP were then applied to poly-
ethylene terephthalate (PET) fabric by exhaustion dyeing method
due to their good hydrophobicity similar to the disperse dyes,
which had affinity to PET fiber and absorbed on it. The dyeing
exhaustion of CBHDCP, CBMPP and Tinuvin 326 on PET fabric have
also been calculated by experimental, and then explained by the
solubility parameter theory.
Proton nuclear magnetic resonance (1H NMR) spectra were re-
corded on a Varian Inova 400 NMR spectrometer (Varian, USA)
with tetramethylsilane (TMS) as internal standard in DMSO-d6.
Infrared spectra were measured with a Fourier Transform–infrared
(FTIR)-430 spectrophotometer (Jasco Co., Japan). Mass spectra (MS)
were recorded on an HP1100 HPLC/MS system (HP Co., USA) using
electrospray ionisation (ESI) mode. Ultraviolet–visible (UV–vis)
absorption spectra were recorded on a Lambda 900 UV–vis spec-
trophotometer (Perkin–Elmer Co., USA).
3.2. Synthesis of CBHDCP and CBMPP
2. Theoretical methodology
The synthesis processes of benzotriazole CBHDCP and CBMPP
are shown in Scheme 1. Firstly, compound 1 and 2 were synthe-
sized from 4-chloro-2-nitroaniline diazonium salts with
N-methyl-3-cyano-6-hydroxy-4-methyl-2-pyridone and 1-phe-
nyl-3-methyl-5-pyrazolone using classical reaction for the synthe-
Density functional theory (DFT) and time dependent (TD) calcu-
lations were done to determine the optimized geometry and UV
absorption spectra. Therefore, in this work, by allowing the relax-
ation of all the parameters, calculation has been found to converge
to a optimized geometry at B3LYP/6-31G(d) level, as revealed by
the absence of imaginary values in the calculated wavenumbers
of all the vibrational modes, while the electronic transition ener-
gies and electronic transition orbital were calculated by B3LYP-
TD/6-31G(d) method. Cluster model and the self-consistent
isodensity polarizable continuum model (SCI-PCM) were used to
explain the UV absorption spectra of CBHDCP in ethanol solution.
All the quantum mechanical calculations in this paper were carried
out in the Gaussian09 program [10].
sis of the azocompounds [12]. Subsequently, compound
1
(0.05 mol) was dissolved in aqueous solution containing NaOH
(0.55 mol) and water (300 mL). The solution was heated and kept
the temperature at about 83 °C, and thiourea dioxide (0.25 mol)
was added in four times within 2 h. After a total reaction time of
3 h, the solution was poured in ice water and acidified to pH 2.0
with concentrated hydrochloric acid, and then the product
CBHDCP was filtered and dried in vacuum. CBMPP was also syn-
thesized using the same process described above where compound
1 was replaced by compound 2. The crude products of CBHDCP and
CBMPP were purified by recrystallisation with ethanol.
5-(5-Chloro-2-benzotriazolyl)-6-hydroxy-1,4-dimethyl-3-car-
bonitrile-2-pyridone (CBHDCP): Yield: 86%. FTIR (ATR/cmꢂ1): 3346
(OH), 2206 (CN), 1643 (C@O), 1106 (CꢂCl). 1H NMR (400 MHz,
DMSO-d6): d 8.11 (s, 1H, Ar–H), 8.02 (d, 1H, Ar–H), 7.46 (d, 1H,
Ar–H), 3.12 (s, 3H, NꢂCH3), 1.68 (s, 3H, CH3). MS (ESI, negative):
m/z 314.4 [(MꢂH)ꢂ, 100%], 316.4 [(MꢂH+2)ꢂ, 36%]. Element anal-
ysis: Found (%): C, 53.21, H, 3.24, N, 22.23; Calcd. (%): C, 53.26; H,
3.19; N, 22.18.
The solubility parameters of UVA were estimated using the
group contribution method according to Eq. (1). For calculating
the solubility parameters of the UVA molecules, the values of cohe-
sive energy (Ecoh) and molar volume (Vm) for each functional group
at 25 °C were obtained from Fedor’s data [11].
ꢀ
ꢁ
1=2
R
R
Ecohi
Vmi
d ¼
ð1Þ
where d is the solubility parameter of a molecule; Ecohi is the cohe-
sive energy for i functional group on the molecule, and Vmi is its
molar volume.
4-(5-Chloro-2-benzotriazolyl)-5-methyl-2-phenyl-3-pyrazolone
(CBMPP): Yield: 88%. FTIR (ATR/cmꢂ1): 2818 (CH3), 1631 (C@O),
HO
CH3
CH3
N
H
N
O
c
d
N
N
N
N
Cl
N
O
O
Cl
NO2
H3C
CN
CN
H3C
b
1
CBHDCP
NH2
NO2
N2
Cl
a
Cl
Cl
NO2
e
O
O
H
N
c
d
N
N
N
N
Cl
N
N
N
N
Cl
NO2
H3C
H3C
2
CBMPP
Scheme 1. Synthetic routes of N-heterocycle-containing benzotriazole compounds. Reagents and conditions: (a) NaNO2/HCl; (b) N-methyl-3-cyano-6-hydroxy-4-methyl-2-
pyridone, Na2CO3, 0–5 °C; (c) thiourea dioxide, NaOH, 83 °C, 3 h; (d) HCl; (e) 1-phenyl-3-methyl-5-pyrazolone, 0–5 °C.

96
Z. Cui et al. / Journal of Molecular Structure 1054–1055 (2013) 94–99
1049 (CꢂCl). 1H NMR (400 MHz, DMSO-d6): d 8.08 (s, 1H, Ar–H),
7.99 (d, 1H, Ar–H), 7.94 (d, 2H, Ar–H), 7.43 (d, 1H, Ar–H), 7.40 (d,
2H, Ar–H), 7.18–7.16 (m, 1H, Ar–H), 2.25 (s, 3H, CH3). MS (ESI, po-
sitive): m/z [348.2(M+Na)+, 100%], [350.2(M+Na+2)+, 39%]. Element
analysis: Found (%): C, 59.06, H, 3.67, N, 21.44; Calcd. (%): C, 58.99,
H, 3.71, N, 21.50.
(2)). The infrared spectrum of benzotriazole CBMPP detected in
solid state shows one intense carbonyl band at about 1631 cmꢂ1
,
which is assigned to the Keto form. Both of them can mainly exist
as or convert to Enol form firstly and absorb UV light by ESIPT
mechanism similar to other 2-(2-Hydroxyphenyl)-benzotriazole
derivatives (Fig. 1). In the 1H NMR spectra of benzotriazole
CBHDCP and CBMPP, the signal corresponding to CH proton reso-
nance of the Keto form does not appear. It indicates benzotriazole
CBHDCP and CBMPP mainly exist as Enol form in DMSO-d6 solu-
tion despite their active hydrogen signal in OH often disappear
due to hydrogen exchange with DMSO-d6.
3.3. Dyeing to PET fabric
Benzotriazole CBHDCP, CBMPP and Tinuvin 326 had been
milled in the presence of a dispersant NNO (1:1 w/w) with glass
beads (1 mm in diameter) for 4 h to form their aqueous suspen-
sion, respectively. Then the aqueous suspensions were applied to
PET fabrics by an exhaustion dyeing at conditions of liquor-to-fab-
ric of 40:1, concentration of 0.5–2.0% on weight of fiber (owf) and
dyebath pH 5.0. Dyeing was started at room temperature and in-
creased to 130 °C at a rate of 2 °C minꢂ1, and held for 1 h before
cooling to room temperature. Then the fabrics were taken out,
rinsed with water and finally air-dried.
4.2. UV–vis absorption spectrum
The UV–vis spectra of the benzotriazole derivatives CBHDCP,
CBMPP and Tinuvin 326 measured in ethanol and chloroform
according to their solubility are shown in Fig. 3(a and b), respec-
tively. As shown in Fig. 3, the maximum absorption wavelength
(kmax) of benzotriazole CBHDCP and CBMPP are at 327 nm in eth-
anol and 340 nm in chloroform, respectively. And only one sharp
peak appears in the range of 280–400 nm, which has great differ-
ence with Tinuvin 326 exhibiting two peaks at about 310 nm and
3.4. Measurement of exhaustion
The UVA in the residual dye bath and staining inside the dyeing
pot were rinsed with acetone and dissolved into 50/50 acetone/
water. The optical absorbance of the solutions was determined
according to Lambert–Beer’s law at the maximum absorption
wavelength of each dye by UV–vis spectrophotometer. Subse-
quently, the exhaustion was calculated using Eq. (2).
350 nm. The molar extinction coefficient (emax) of benzotriazole
CBHDCP (27,000 L molꢂ1 cmꢂ1 at 327 nm in ethanol) and benzotri-
azole CBMPP (28,500 L molꢂ1 cmꢂ1 at 340 nm in chloroform) is
much larger than that of Tinuvin 326 (18,900 L molꢂ1 cmꢂ1 at
351 nm in ethanol, 16,300 L molꢂ1 cmꢂ1 at 353 nm in chloroform).
Quantum chemistry method TD DFT has been used to simulate
the UV–vis absorption spectra successfully [13–15]. In this paper,
the UV absorption data of two synthesized N-heterocycle-contain-
ing benzotriazole UVAs (CBHDCP and CBMPP) were analyzed by
quantum chemistry calculations. The TD calculation results about
electronic absorption band, oscillator strength, molar extinction
coefficient and maximum absorption wavelength above 250 nm
wavelength range are listed in Table 1. As shown in Table 1, based
on gas monomolecular model, the two UVAs display high calcu-
lated maximum molar extinction coefficient 21,000 L molꢂ1 cmꢂ1
(CBHDCP) and 27,000 L molꢂ1 cmꢂ1 (CBMPP) as well as strong
absorption range in 280–380 nm UV region, matching ideal UV
absorption properties.
Exhaustion ð%Þ ¼ ½ðA1 ꢂ A2Þ=A1ꢃ ꢄ 100%
ð2Þ
where A1 and A2 are the absorbance of the dye bath dissolved into
50/50 acetone/water before and after dyeing.
4. Results and discussion
4.1. Synthesis and characteristic
Both benzotriazole CBHDCP and CBMPP may exist in different
tautomeric forms (Enol form and Keto form) under unexcited
states (Fig. 2). The infrared spectrum of benzotriazole CBHDCP de-
tected in solid state shows one broad hydroxyl band at about
3346 cmꢂ1, which is assigned to the Enol form (Enol (1) or Enol
The agreement between the simulated S0 ? S1 electronic tran-
sition band of CBHDCP and CBMPP in their Enol forms and the
Cl
Cl
Cl
Cl
hv
N
N
N
N
N
N
N
N
N
N
N
N
H
O
N
O
N
N
O
N
O
H
H3C
NC
O
H3C
NC
O
H3C
NC
OH
H3C
NC
CH3
CH3
CH3
CH3
OH
CBHDCP-Keto
CBHDCP-Enol(1)
CBHDCP-Enol(2)
Cl
Cl
Cl
N
N
N
N
N
N
N
N
H
N
hv
H
OH
H3C
O
O
H3C
H3C
N N
N
N
N
N
CBMPP-Keto
CBMPP-Enol
Fig. 2. The tautomerism between keto and Enol forms of CBHDCP, CBMPP and their UV absorbing mechanism.

Z. Cui et al. / Journal of Molecular Structure 1054–1055 (2013) 94–99
97
0.6
0.6
0.5
0.4
0.3
0.2
0.1
0.0
340nm
327 nm
(a)
(b)
CBMPP
Tinuvin 326
0.5
0.4
0.3
0.2
0.1
0.0
CBHDCP
Tinuvin 326
351 nm
310 nm
353nm
313nm
280
320
360
400
440
280
320
360
400
440
Wavelength (nm)
Wavelength (nm)
Fig. 3. UV–vis absorption spectra of benzotriazole CBHDCP, CBMPP and Tinuvin 326. (a) in ethanol (2 ꢄ 10ꢂ5 mol/L); (b) in chloroform (2 ꢄ 10ꢂ5 mol/L).
Table 1
TD calculation results about electronic absorption band, oscillator strength, molar extinction coefficient and maximum absorption wavelength above 250 nm wavelength range.
Transition state
Oscillator strength (f)
Molar extinction coefficient (L molꢂ1 cmꢂ1
)
Maximum absorption wavelength (nm)
Calcd.
Expt.
Calcd.
Expt.
Tinuvin 326
S0 ? S1
S0 ? S2
S0 ? S3
S0 ? S4
0.2574
0.4135
0.0595
0.0190
14,000
18,900 (ethanol), 16,300 (chloroform)
376
315
291
251
353 (ethonal) 355 (chloroform)
310 (ethonal) 313 (chloroform)
CBHDCP-Enol(1)
S0 ? S1
S0 ? S2
S0 ? S3
S0 ? S4
S0 ? S5
S0 ? S6
S0 ? S7
0.1781
0.1016
0.0405
0.0755
0.0220
0.0105
0.0294
12,000
311
302
280
274
267
262
253
CBHDCP-Enol(2)
S0 ? S1
S0 ? S2
S0 ? S3
S0 ? S4
S0 ? S5
S0 ? S6
S0 ? S7
0.5098 (0.6291)
0.1494 (0.0918)
0.0471 (0.0455)
0.0002 (0)
0.1452 (0.0109)
0.0062 (0.0901)
0.0002 (0.0002)
21,000 (25,500)
27,000 (ethonal)
373 (349)
313 (297)
296 (280)
280 (274)
267 (261)
260 (261)
256 (259)
327 (ethonal)
CBHDCP-Keto
S0 ? S1
S0 ? S2
S0 ? S3
S0 ? S4
S0 ? S5
S0 ? S6
S0 ? S7
0.0002
0.0130
0.0078
0.1098
0.0260
0.0128
0.1956
348
308
302
282
265
264
262
CBMPP-Enol
S0 ? S1
S0 ? S2
S0 ? S3
S0 ? S4
0.5738
0.1791
0.0551
0.0034
0.1282
27,000
28,500 (chloroform)
342
328
286
274
252
340 (chloroform)
S0 ? S5
CBMPP-Keto
S0 ? S1
S0 ? S2
S0 ? S3
S0 ? S4
S0 ? S5
S0 ? S6
S0 ? S7
S0 ? S8
0.0120
0.0217
0.0016
0.1460
0.0014
0.0109
0.2845
0.0002
339
318
285
284
274
270
268
265
Note: The data in parentheses are obtained based on cluster model and SCI-PCM solution model, and other calculation results are based on gas monomolecular model.
experimental spectra (CBHDCP: 27,000 L molꢂ1 cmꢂ1 at 327 nm in
ethanol, CBMPP: 28,500 L molꢂ1 cmꢂ1 at 340 nm in chloroform) is
excellent, as shown in Table 1. Therefore both CBHDCP in ethanol
and CBMPP in chloroform are Enol form, which agree with the 1H
NMR characterization results. The optimized structures of CBHDCP
in ethanol and CBMPP in chloroform in Enol form are shown in
Fig. 4. Fig. 4 clearly shows that the skeleton cyclic structure of
CBHDCP-Enol(2) are in different planes, but the skeleton structure

98
Z. Cui et al. / Journal of Molecular Structure 1054–1055 (2013) 94–99
Table 3
The solubility parameters of CBHDCP, CBMPP and Tinuvin 326 estimated using the
group contribution method.
Data
CBHDCP-Enol CMMPP-Keto Tinuvin 326 PET
Ecoh
Vm
173768
137
154165
156.2
31.4
147866
175
29.1
—
—
23.5
Solubility parameter 35.6
The solubility parameter of PET was calculated based on Ecoh and Vm values from
Hoy.
dyed fabric samples with UVA provided effective protection
against UVR. The application of benzotriazole CBHDCP at 0.5%
owf increased the ultraviolet protection factor (UPF) to 62 (the
UPF of blank PET fabric is only 37). However, with the amount
increase of benzotriazole CBHDCP to 1.0% owf and even 2.0%
owf, no obvious UPF increase for PET fabric was found which
may be induced by their poor exhaustion (less than 11%). On the
contrary, benzotriazole CBMPP has better exhaustion on PET fabric
(more than 50%) than CBHDCP. The application of benzotriazole
CBMPP at 0.5% owf sharply increased the UPF over 180. The UPF
of PET fabric reached 380 with the application of benzotriazole
CBMPP at 2.0% owf, which is close to the ultraviolet protection ef-
fect of Tinuvin 326 on PET at 1.0% owf even though the exhaustion
of CBMPP (51%) is much lower than that of Tinuvin 326 (93.5%).
The higher UPF of the dyed PET fabric means benzotriazole CBMPP
is much superior to benzotriazole CBHDCP and acts as an effective
UVA due to its combinative higher exhaustion and higher molar
extinction coefficient compared with benzotriazole CBHDCP.
The solubility parameter is commonly used to predict the solu-
bility of one solid or liquid in another liquid. Similarly, the concept
can be also introduced to predict the dissolution of hydrophobic
UVA in a solid solvent such as PET, namely, exhaustion of UVA
on PET. It was found that the hydrophobic small molecules with
high sorption on PET tend to have solubility parameters near that
of PET, d 23.5 (J/cm3)0.5. The solubility parameters of CBHDCP,
CBMPP and Tinuvin 326 have been estimated using the group
contribution method according to Eq. (1). Table 3 shows the solu-
bility parameters of CBHDCP, CBMPP, Tinuvin 326 and PET. It is
clearly presented in Tables 2 and 3 that the solubility parameters
decrease in the order of CBHDCP > CBMPP > Tinuvin 326 > PET,
and the exhaustion on PET increase in the order of
CBHDCP < CBMPP < Tinuvin 326. The result agrees with previous
studies that disperse dyes with high exhaustion on fiber have
solubility parameters close to that of polymer.
Fig. 4. The optimized structures of CBHDCP-Enol(2) and CBMPP-Enol at B3LYP-
TD/6-31G(d) theoretical level.
Fig. 5. Cluster model of CBHDCP-Enol—CH3CH2OH.
of CBMPP-Enol is planar with Cs symmetry. As for CBHDCP-
Enol(2) with cyclic ketone structure, the carbonyl group interac-
tion with protic solvents such as ethanol by hydrogen bond
influence its UV absorption spectrum significantly. Herein, the
hydrogen bond interaction and solvent polar effect should be con-
sidered for calculating UV–vis absorption spectrum of CBHDCP in
ethanol solution.
Subsequently, cluster model (Fig. 5) for hydrogen bond interac-
tion and self-consistent isodensity polarizable continuum model
(SCI-PCM) for solvent polar effect have been selected, as Table 1
listed. As the data in parentheses of Table 1 shown, the model
which considers the hydrogen bond interaction and solvent polar
effect can give more anastomotic results on molar extinction coef-
ficient and maximum absorption wavelength in comparison with
the experimental results.
5. Conclusions
Two highly efficient benzotriazole absorbers CBHDCP and
CBMPP with single sharp absorption in
a narrow range of
300–360 nm as well as strong absorption ability were successfully
synthesized, and their structures were confirmed by FT-IR, 1H
NMR, mass spectroscopy, elemental analysis and quantum chemis-
try calculations. Systematic quantum chemistry calculations were
performed to investigate the UV electronic absorption bands of
4.3. Exhaustion and UPF
The exhaustion and UV protection data of CBHDCP, CBMPP and
Tinuvin 326 on PET fabric were listed in Table 2. It was clear that all
Table 2
Exhaustion and UPF data recorded on dyed PET fabric.
Owf/%
Benzotriazole CBHDCP
Benzotriazole CBMPP
Tinuvin 326
Exhaustion/%
Exhaustion/%
UPF
Exhaustion/%
UPF
UPF
0.5
1.0
2.0
10.9
5.4
3.9
62
67
75
63.2
56.9
51.0
183
226
380
97.2
93.5
75.6
294
385
440
The UPF of blank PET fabric is 37.

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CBHDCP and CBMPP and found out the excellent absorption of
CBHDCP and CBMPP come from S0 ? S1 electronic transition band
of the Enol structures. To CBHDCP-Enol, the hydrogen bond inter-
action and solvent polar effect should be considered to simulate
the UV absorption spectrum for its cyclic ketone structure. It was
clear that the dyed fabrics by CBHDCP and CBMPP provided effec-
tive protection against UVR. Furthermore, the analysis about the
solubility parameter of CBHDCP and CBMPP gave reasonable
explanation for the exhaustion’s difference for the two UVAs on
PET fabrics. This work appears that cowork of quantum chemistry
calculations and organic synthesis is very powerful to develop
highly effective UV absorbers.
Acknowledgments
This work was supported by Zhejiang Provincial Key Innovation
Team (No. 2010R50038), the National Natural Science Foundation
of China (Nos. 21106135 and 51173168) and ‘‘521’’ talent cultiva-
tion of Zhejiang Sci-Tech University.
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