DFT Calculation of the Absorption Properties of Brown Carbon

Subscriber access provided by UNIV OF NEWCASTLE

Article

DFT Calculation of the Absorption Properties of Brown Carbon Chromophores Generated by Catechol Heterogeneous Ozonolysis Ana Catarina O. Magalhães, Joaquim C.G. Esteves da Silva, and Luís Pinto da Silva ACS Earth Space Chem., Just Accepted Manuscript • DOI: 10.1021/ acsearthspacechem.7b00061 • Publication Date (Web): 10 Jul 2017 Downloaded from http://pubs.acs.org on July 18, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Earth and Space Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Earth and Space Chemistry

1

DFT Calculation of the Absorption Properties of

2

Brown Carbon Chromophores Generated by

3

Catechol Heterogeneous Ozonolysis

4

Ana Catarina O. Magalhães,1,2 Joaquim C.G. Esteves da Silva1,2 and Luís Pinto da Silva1,2*

5

1

6

Sciences of University of Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.

7

2

8

Sciences of University of Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.

Chemistry Research Unit (CIQUP), Department of Chemistry and Biochemistry, Faculty of

LACOMEPHI, Department of Geosciences, Environment and Territorial Planning, Faculty of

9

10

ABSTRACT. The effect of light-absorbing atmospheric particles on climate change has been

11

incorporated into climate models, but the absence of brown carbon (BrC) in these models has

12

been leading to significant differences between model predictions and measured data on radiative

13

forcing. Also, little is known regarding the relationship between optical properties and BrC’s

14

chemical compositions. Thus, we have characterized the absorption properties of catechol and

15

known heterogeneous ozonolysis products, with a theoretical approach based on Density

16

Functional Theory (DFT). While catechol presents a weak absorption maximum in the UVC

17

region, other polyaromatic derivatives present an absorption up to six times higher, with

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 28

18

biphenyl-2,2’,3,3’-tetraol, biphenyl-3,3’,4,4’,5,5’-hexaol and terphenyl-2’,3,3’,3’’,4,4’’-hexaol

19

presenting the strongest absorption. Moreover, these derivatives now absorb in the UVB and

20

UVA regions, which are types of actinic radiation in the UV region not filtered by atmosphere

21

(contrary to UVC), with terphenyl molecules presenting the highest absorption maximum.

22

Furthermore, the absorption efficiency of these compounds is potentiated in the condensed

23

phase, such as cloud droplets, rain, fogs, and water films, due to a higher degree of electron

24

delocalization. This study provides reliable information regarding the absorption properties of

25

BrC generated by catechol, which is essential for the development of accurate models of climate

26

forcing.

27

KEYWORDS. Catechol; Ozonolysis; Brown Carbon; Climate Change; Density Functional

28

Theory; Polyhydroxylated Biphenyl; Polyhydroxylated Terphenyl.

29 30

TABLE OF CONTENTS GRAPHIC.

31 32


2

Page 3 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


33

INTRODUCTION

34

Atmospheric aerosols have an important role in Earth’s radiative balance, due to their ability to

35

scatter and absorb solar radiation.1-3 The most well-known type of light-absorbing carbonaceous

36

aerosol is called “black carbon” (BC), which is generated by fossil fuel combustion and biomass

37

burning.4-6 In fact, BC has already been incorporated into climate models.7,8 However, there still

38

exist significant differences between model predictions and measured data on aerosol absorption

39

and radiative forcing.3,9

40

These discrepancies can be partially explained by the absence in these models of atmospheric

41

“brown carbon” (BrC), a light-absorbing form of organic aerosol components.3,10-14 BrC is able

42

to strongly absorb solar radiation in the UV and (sub)visible wavelengths, which affects the

43

overall atmospheric energy distribution.10,11 Nevertheless, many global models still consider

44

organic particulates to only participate in light scattering.10,15

45

Despite these shortcomings in climate models, BrC is starting to be recognized as a significant

46

contributor to light absorption and climate forcing.3,10 A model simulation made by Feng and co-

47

workers indicated that atmospheric BrC is responsible for 7-19% of the total aerosol absorption.5

48

Other global models estimate that light absorption by BrC in different regions of the world may

49

account for 27-70% of the BC light absorption.14,16 Some authors even state that BrC can

50

dominate aerosol absorption, either at specific wavelengths or in certain regions of the Earth.3,9,17

51

While BrC is essential for understanding climate forcing, making quantitative predictions of the

52

BrC contribution to the overall light absorption is a challenging task.

53

The absorption properties of organic compounds depend on their molecular structure. However,

54

little is known regarding the relationship between the chemical composition of BrC and its


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 28

55

absorption properties.3 Moreover, the optical properties of BrC evolve significantly as a result of

56

atmospheric processes such as oxidation and solar irradiation (leading to photochemical

57

reactions).18-20 These factors make the composition and concentration of BrC chromophores

58

highly variable across sources and locations,3,11 resulting in high uncertainties in predicting and

59

mitigating the climate effects of BrC.21,22

60 61

Figure 1 - Schematic representation of catechol and its phenyl derivatives.

62

Dihydroxybenzenes such as catechol are the most common gas-phase organic compounds (~50

63

ppbv) resulting from biomass pyrolysis, combustion and burning.23,24 Cloud water collected from

64

brown clouds also contain aromatic compounds.25 The surfactant properties of these species

65

favor the presence of these compounds at the interface of aerosols.26 Given this, some attention

66

has been given to the processing of catechol under humid tropospheric conditions.26-28 One such

67

processing pathway is heterogeneous ozonolysis.26-28 Indirect oxidation by hydroxyl radicals

68

results in the formation of semiquinone radicals toward the synthesis of polyhydroxylated rings


4

Page 5 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


69

(Figure 1).26-28 Heterogeneous ozonolysis also produces heavier polyhydroxylated biphenyl and

70

terphenyl compounds (Figure 2), which result from the coupling of semiquinone radicals.26-28

71

While these works are essential for understanding the formation of secondary organic aerosols

72

(SOAs) derived from catechol,26-28 no information was provided regarding the optical properties

73

of the catechol-derived SOAs, which prevents the characterization of the relationship between

74

BrC and its absorption properties.

75 76

Figure 2 - Schematic representation of catechol and its biphenyl and terphenyl derivatives.

77

Herein, the objective of this work is to characterize the optical properties of known

78

polyhydroxylated benzene, biphenyl and terphenyl SOAs derived from catechol (Figures 1 and

79

2). Such information is essential for developing global models able to predict and mitigate the


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 28

80

climate effects of BrC. To this end, we present Density Functional Theory (DFT) calculations on

81

14 SOAs and 1 parent compound (catechol). DFT calculations have become a reliable and

82

essential tool in environmental chemistry, providing detailed information regarding reaction

83

mechanisms, energetics, transition states and absorption properties.29-34 This is achieved with

84

efficiency gains in experimental approaches, as there is no need for a high number of steps such

85

as chemical synthesis, separation and purification, and characterization processes. DFT

86

calculations therefore allow us to determine the absorption properties of these compounds and

87

identify the SOAs expected to have more important roles in climate forcing.

88 89

COMPUTATIONAL METHODS

90

All calculations were performed with the Gaussian 09 program package35 at two levels of theory.

91

Geometry optimizations were made with the PBE0 density functional36 and the 6-31G(d,p) basis

92

set. Vibrational calculations were made, at the same level of theory, in order to ensure that the

93

obtained structure were minima in their potential energy surfaces (PES). The PBE0 functional

94

was used due to previous accurate results in the geometry optimization of organic compounds.37-

95

39

96

The absorption properties (absorption wavelengths and respective oscillator strengths) were

97

obtained by performing single point calculations, at the PW91PW91/6-31+G(d,p) level of

98

theory,40 on the structures obtained at the PBE0/6-31G(d,p) level of theory. The absorption

99

properties were obtained by using a time-dependent (TD) DFT approach.41 The PW91PW91

100

density functional was chosen due to what was previously reported by other authors, who have


6

Page 7 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


101

showed that this method is able to describe the absorption properties of catechol with a

102

reasonable accuracy.42

103

The absorption properties of catechol (and other polyphenols) were already studied at the TD-

104

DFT level of theory by Trouillas and co-workers.43 They tested a wide class of functionals from

105

pure to hybrid functionals (including more or less HF exchange), but have found that these DFT

106

methods significantly over-estimated the absorption wavelength maximum of catechol (by 1.40-

107

2.33 eV). They have also found that the results were not significantly improved by increasing the

108

basis set used, albeit a slight increase (about 0.2 eV) was achieved by the inclusion of diffuse

109

functions.43 Another paper, this time made by Ashford and co-workers,42 showed that the

110

PW91PW91 exchange-correlation functional could reproduce adequately the major features in

111

the absorption spectrum of catechol. Furthermore, they have showed that the excitation energy of

112

the Franck-Condon bright state is relatively insensitive to the basis set used with this functional,

113

with a slight improvement coming from the inclusion of diffuse functions in the basis set.42

114

Given this, the PW91PW91 was chosen to calculate the absorption properties of catechol and

115

derivatives. The chosen basis set was 6-31+G(d,p) because it is a basis set including diffuse

116

functions, which presents a good balance between accuracy and required computational power.

117

All geometry optimizations and frequency calculations were made in the gas phase. The

118

absorption properties were calculated both in the gas phase or in aqueous solvent, simulating

119

atmospheric aerosol particles present in cloud droplets, rain, fogs, and water.29 The water

120

medium was modelled by using the integral equation formalism implicit solvation model

121

(IEFPCM).44


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

122

The orbitals that contribute to the absorption spectrum, and the charge density were visualized

123

with the MultiWFN program package.45 The absorption spectra were plotted with the SpecDis

124

software.46

Page 8 of 28

125 126

RESULTS AND DISCUSSION

127

The theoretical absorption wavelength and oscillator strength for the bright Franck-Condon state

128

of catechol, in water, were of 266 nm and 0.1109 (respectively). These values confirm the

129

accuracy of the used TD-DFT approach, as the theoretical absorption wavelength only differed

130

by 0.17 eV from the experimental value (276 nm), which is within the 0.20 eV error limit

131

attributed to TD-DFT methods.37-39,43 In the gas phase, the theoretical absorption wavelength is

132

very similar (264 nm), but the oscillator strength is an order of magnitude lower (0.0449). Thus,

133

the absorption wavelength maximum of catechol is present in the UVC region (~200-290 nm),

134

which is a type of solar radiation considered to be completely filtered by the atmosphere.

135

Moreover, while in the gas phase the absorption of catechol is quite limited, in condensed phase

136

there is an increase in absorption. Further analysis demonstrates that the excitation to the bright

137

state, in both gas and aqueous phase, corresponds mainly to a π→π* transition between the

138

HOMO and LUMO orbitals (Figure 3). The theoretical absorption wavelength and oscillator

139

strength for the bright Franck-Condon state of catechol, in water, were also calculated at the

140

PBE0/6-31+G(d,p) level of theory. The resulting wavelength maximum was of 246 nm and the

141

oscillator strength of 0.1268. Contrary to the PW91PW91 functional, the PBE0 functional

142

provided values that differed from the experimental data by 0.54 eV, which is well outside of the


8

Page 9 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


143

typical error attributed to TD-DFT methods.37-39,43 This supported our use of the PW91PW91

144

functional for determining the absorption properties of catechol and derivatives.

145 146

Figure 3 - Orbital composition of the bright state of catechol and important terphenyl and

147

biphenyl derivatives, in aqueous phase. The green part correspond to positive orbital

148

wavefunctions, while the blue part to negative ones.

149

Having determined the theoretical absorption properties of catechol, both in aqueous and gas

150

phase, we now focus on the properties of its heterogeneous oxidation products. More

151

specifically, we focus on simple hydroxylated oxidation products (Figure 1).26-28 In the gas phase

152

(Table 1), hydroxylation results in an increase of increases the wavelength maximum of the

153

bright state by 7-32 nm, with the exception being 1,2,3-trihydroxybenzene. Given this, only

154

tetrahydroxybenzene 1 presents a wavelength maximum outside of the UVC region, being now

155

in the UVB region (~290-320 nm). The UVB radiation should be more problematic than UVC,


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 28

156

as it is not filtered by the atmosphere and can reach the Earth’s surface (about 5% of actinic

157

radiation in the UV region). However, the oscillator strengths of the bright states of catechol and

158

all hydroxylated derivatives are low. So, their ability to absorb solar radiation in the gas phase is

159

very limited, and should not have a significant impact on climate forcing.

Table 1 - Theoretical absorption wavelength maximum (λabs, in nm) and oscillator strength (f) for catechol and its polyhydroxylated-benzene derivatives (Figure 1), at the PW91PW91/631+G(d,p) level of theory in aqueous phase (aq) and gas phase (g). Molecule

λabs,aq (nm)

λabs,g (nm)

fg

faq

1,2,3,-trihydroxybenzene

236

259

0.0681

0.0039

Catechol

266

264

0.1109

0.0449

tetrahydroxybenzene 1

273

271

0.0676

0.0253

pentahydroxybenzene

277

275

0.0896

0.0387

1,2,4-trihydroxybenzene

289

288

0.1392

0.0652

tetrahydroxybenzene 2

299

296

0.1724

0.0859

160 161

Performing calculations in the aqueous instead of gas results in insignificant changes in the

162

theoretical absorption wavelength of the bright state. The exception was 1,2,3-hydroxybenzene.

163

Major differences were only seen in the oscillator strength. Hydroxylation decreased the

164

oscillator strength (when comparing with catechol) of 1,2,3-hydroxybenzene,

165

tetrahydroxybenzene 1 and pentahydroxybenzene by 39%, 39% and 19% (respectively). The

166

oscillator strength of 1,2,4-hydroxybenzene and tetrahydroxybenzene 2 increased by 26% and

167

55% (respectively). These data indicate that the formation of tetrahydroxybenzene 2 has a more


10

Page 11 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


168

significant impact on climate forcing than the remaining hydroxylated catechol derivatives.

169

While these derivatives absorb solar radiation in the UVC region, the wavelength maximum of

170

tetrahydroxybenzene 2 is present in the UVB region. Moreover, the absorption intensity of

171

tetrahydroxybenzene 2 is 55% higher than catechol. Table 2 - Dihedral angle (ϴ, in º, as seen in Figure 2) and bond length (C-C, in Å) between the carbon atoms connecting the different rings of biphenyl and terphenyl compounds (as seen in Figure 2). Molecule

ϴ1 (º)

ϴ2 (º)

CA-CB (Å)

Biphenyl-2,2’,3,3’-tetraol

-45.4

1.481

Biphenyl-2,3,3’,4’-tetraol

-41.4

1.480


-37.4

1.478

Biphenyl-2,2’,3,3’,4,4’-

-57.4

1.481

-52.2

1.482

-46.3

1.479

-37.4

1.479

CB-CC (Å)

hexaol Biphenyl-2,3,3’,4’,5’,6hexaol Biphenyl-2,3,3’,4’,4,5’hexaol Biphenyl-3,3’,4,4’,5,5’hexaol Terphenyl-2,2’,2’’,3,3’,3’’-

-43.7

43.9

1.480

1.479


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 28

hexaol Terphenyl-2’,3,3’,3’’,4,4’’-

-40.5

48.5

1.479

1.479

hexaol 172 173

The next objective of this study was to assess the absorption properties (Table 3) of biphenyl

174

catechol derivatives (Figure 2), in both gas and aqueous phase. Such compounds are formed by

175

the coupling of semiquinone catechol and polyhydroxylated-benzene radicals.26-28 Some

176

geometrical parameters of these molecules are seen in Table 2. None of these molecules is

177

planar, as the dihedral angle between the two rings ranges from -37º to -57º. Moreover, if we

178

compare the absorption wavelength maximum within the sets of biphenyl-tetraol and biphenyl-

179

hexaol with the dihedral angles, we can see that the absorption maximum is inversely

180

proportional to the dihedral angle. The length of the carbon-carbon bond, connecting the two

181

rings, is between that of a single and a double bond, indicating a degree of delocalization

182

between the phenyl moieties. The predicted conjugation across this bond should make internal

183

rotation energetically unfavorable, and so, prevent significant changes in the dihedral in the

184

ground state.

185

The absorption wavelength maxima of these biphenyl molecules are higher than that of catechol

186

by 24-54 nm (in the gas phase) and by 22-59 nm (in the aqueous phase). With this increase due

187

to change of state, the absorption spectra of basically all molecules shift from the UVC region to

188

the UVB region. Some molecules are even able to absorb now in the UVA region (320-400 nm),

189

which corresponds to 95% of the actinic radiation in the UV region reaching Earth’s surface.

190

This UV region might be the most problematic for climate forcing caused by BrC, in the UV

191

region of actinic radiation, given that it is the region corresponding to the majority of this type of


12

Page 13 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


192

radiation. The molecules that absorb in the UVA region are biphenyl-3,3’,4,4’-tetraol (Figure 4),

193

biphenyl-2,3,3’,4’-tetraol (Figure 4) and biphenyl-3,3’,4,4’,5,5’-hexaol (Figure 4).

Table 3 - Theoretical absorption wavelength maximum (λabs, in nm) and oscillator strength (f) for catechol and its biphenyl and terphenyl derivatives (Figure 2), at the PW91PW91/631+G(d,p) level of theory in aqueous phase (aq) and gas phase (g). λabs,aq (nm)

λabs,g (nm)

faq

fg

Catechol

266

264

0.1109

0.0449


288

288

0.5832

0.1307

Biphenyl-2,2’,3,3’,4,4’-hexaol

299

295

0.3979

0.1294

Biphenyl-2,3,3’,4’,5’,6-hexaol

309

299

0.3640

0.0671

Biphenyl-2,3,3’,4’,4,5’-hexaol

310

305

0.4858

0.1775

Biphenyl-3,3’,4,4’,5,5’-hexaol

320

307

0.6343

0.3358

Biphenyl-2,3,3’,4’-tetraol

321

318

0.3903

0.0925


325

319

0.4730

0.1479

Terphenyl-2,2’,2’’,3,3’,3’’-hexaol 332

354

0.4743

0.2797

Terphenyl-2’,3,3’,3’’,4,4’’-hexaol 362

374

0.6784

0.1418

194 195

Another important result is that the biphenyl derivatives have all significantly higher oscillator

196

strength than catechol, both in the gas phase and aqueous phase. In fact, the oscillator strength of

197

these oxidation products is around two to six times higher than that of catechol. This means that

198

these compounds absorb more UV radiation than catechol, and thus, the atmospheric processing


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

199

of catechol leads to SOAs with a more important role on climate forcing than the parent

200

molecule.

Page 14 of 28

201 202

Figure 4 - Comparative theoretical absorption spectra between catechol and biphenyl-3,3’,4,4’-

203

tetraol, biphenyl-2,3,3’,4’-tetraol, biphenyl-3,3’,4,4’,5,5’-hexaol, terphenyl-2’,3,3’,3’’,4,4’’-

204

hexaol and terphenyl-2,2’,2’’,3,3’,3’’-hexaol, in condensed phase.

205 206

As with the single-ring polyhydroxylated derivatives, re-calculating the absorption wavelength

207

of biphenyl compounds in the aqueous state does not significantly change it from the gaseous

208

state. However, the oscillator strength of the bright state increases. One factor that does not

209

appear to correlate with absorption properties of these compounds is their degree of

210

hydroxylation.


14

Page 15 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


211

Finally, we focused on catechol oxidation products consisting of terphenyl compounds. Their

212

geometrical parameters can be found in Table 2. The conclusions that can be reached with these

213

results are the same as for biphenyl compounds. None of this molecule is planar, and the

214

absorption wavelength maximum is inversely proportional to the dihedral angle of rings A and B

215

(Figure 2). The calculated bond lengths also show electron delocalization between the phenyl

216

moieties. Their calculated absorption properties, both in the gas and aqueous phase, are present

217

in Table 3. Coupling of three semiquinone catechol radical rings leads to a significant increase of

218

the absorption wavelength maximum (Figure 4), by 66-110 nm. Thus, the absorption spectra of

219

both terphenyl derivatives reside clearly in the UVA region. The oscillator strength is also

220

affected by the coupling of three rings, as it is now between three and six times higher than the

221

one presented by catechol. The inclusion of solvation once again increases the oscillator strength

222

of bright states, when compared with the gas phase. However, for terphenyl molecules solvation

223

also decreases the absorption wavelength maximum by 12-22 nm. Nevertheless, in aqueous

224

phase both terphenyl molecules still absorb in the UVA region.

225

Having analyzed the absorption properties of catechol and its heterogeneous oxidation

226

products,26-28 we conclude that the atmospheric processing of catechol can have a significant

227

impact on climate forcing. While catechol absorbs weakly UVC solar radiation, several oxidation

228

products (mainly biphenyl and terphenyl ones) are able to absorb UVB and even UVA radiation.

229

Moreover, these new compounds absorb much more strongly than catechol, up to a factor of six

230

times. However, the involvement of these new compounds in climate forcing is expected to be

231

more significant when they are present in wet aerosols, and not when present in the gas phase.

232

It should be noted that the present calculations showed that the polyhydroxylated phenyl,

233

biphenyl and terphenyl products of catechol heterogeneous oxidation absorb light in the UV-


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 28

234

visible region (between ~200 and ~400 nm). However, an experimental study performed by

235

Ofner et al showed that SOAs derived from catechol are able to absorb between ~200 nm and

236

~600 nm.47 Thus, actual catechol SOAs absorb much further out into the visible than any

237

individual compound resulting from catechol heterogeneous oxidation. One possible explanation

238

is that the absorption properties of BrC is not determined only by the sum of the absorption

239

properties of each one of its individual constituents, but is also determined by interactions

240

between these compounds. This is in line with the work of Phillips and Smith, who have found

241

that charge transfer complexes can be a significant source of light absorption by organic

242

compounds in aerosols.48

243

Nevertheless, in order to ensure that this higher extension into the visible in not simply caused by

244

the presence of linear oxidation products, we have also calculated the condensed-phase

245

absorption spectrum of cis,cis-muconic acid. This compound was found to be the dominant

246

product of heterogeneous ozonolysis of thin film catechol at several relative humidites.49 The

247

neutral species present a absorption maximum at 289 nm, with an oscillator strength of 0.6024.

248

Thus, it do not appears to be this species to explain the absorption of catechol-derived SOAs at

249

wavelengths higher than 400 nm. Nevertheless, it should be noted that due to the high oscillator

250

strength of cis,cis-muconic acid, this species should be very important for the absorption of

251

catechol-derived SOAs in the UV-visible region.


16

Page 17 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


252 253

Figure 5 - Difference between the charge density of the ground and bright states, in water, of

254

terphenyl-2’,3,3’,3’’,4,4’’-hexaol and terphenyl-2,2’,2’’,3,3’,3’’-hexaol. The green part

255

corresponds to an increase in electron density, while the blue one corresponds to a decrease.

256 257

We compared the catechol derivatives with high absorption wavelengths and oscillator strengths,

258

in condensed phase. The compound with both the highest absorption wavelength (362 nm) and

259

oscillator strength (0.6784) is terphenyl-2’,3,3’,3’’,4,4’’-hexaol. The bright state of this molecule

260

is a π→π* state, composed by a HOMO → LUMO orbital transition. Both orbitals are


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 28

261

significantly delocalized throughout the terphenyl structures, and more, they present a significant

262

orbital overlap between the HOMO and LUMO. The delocalization and overlapping indicate the

263

formation of π-π conjugation between the three moieties of terphenyl-2’,3,3’,3’’,4,4’’-hexaol,

264

which then accounts for a higher wavelength maximum and a higher efficiency of transition.33,50-

265

52

266

from the right to the left ring. This is supported by the calculation of the dipole moment of the

267

ground and bright states, which increased from 0.83 to 13.38 Debye, respectively. The difference

268

in charge density between the ground and bright states are presented in Figure 5.

269

Terphenyl-2,2’,2’’,3,3’,3’’-hexaol presents the second highest absorption wavelength (332 nm)

270

from all derivatives, but only the fifth highest oscillator strength (0.4743), albeit still being a very

271

high efficiency of transition. Once again, the bright state of this molecule is a π→π* state, this

272

time composed mainly by a HOMO(-2) → LUMO orbital transition. These orbitals are also

273

delocalized throughout the terphenyl structure, indicating the formation of π-π conjugation.

274

However, in HOMO(-2) the delocalization is more evident in the center and right ring. The lower

275

orbital overlap in the left ring should explain the lower oscillator strength of this molecule, when

276

compared with terphenyl-2’,3,3’,3’’,4,4’’-hexaol.33,50-52 This is supported by the charge density

277

between the ground and bight states, as the difference is present mainly in the center and right

278

rings.

279

The catechol oxidation product with the third highest absorption wavelength is biphenyl-

280

3,3’,4,4’-tetraol (325 nm) and has the sixth highest oscillator strength (0.4730). The bright state

281

is also a π→π* state, composed mainly by a HOMO → LUMO orbital transition. There is also a

282

delocalization and orbital overlap of π orbitals, thereby providing an explanation for its high

283

wavelength maximum and oscillator strength. Biphenyl-3,3’,4,4’,5,5’-hexaol (with an absorption

The HOMO → LUMO transition also points to the occurrence of a charge density transfer


18

Page 19 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


284

wavelength of 320 nm) presents the second highest oscillator strength (0.6343), and its bright

285

state is also a π→π* state composed mainly by a HOMO → LUMO orbital transition. Finally,

286

biphenyl-2,2’,3,3’-tetraol (with a wavelength maximum of 288 nm) is catechol derivative with

287

the third higher efficiency of transition (0.5832). Its bright state is also a π→π* state composed

288

mainly by a HOMO(-2) → LUMO orbital transition, with significant delocalization. Thus, the

289

formation of π-conjugation and orbital overlap between HOMO(x) and LUMO is essential for

290

obtaining high values of the absorption wavelength maximum and oscillator strength.33,50-52

291

In conclusion, while catechol is a molecule that absorbs weakly in the UVC region (~200-290

292

nm), oxidation leads to the formation of products with significantly stronger absorption. In fact,

293

biphenyl and terphenyl derivatives present absorption intensities up to six times higher than

294

catechol, which indicate that these species are expected to have a more significant role on

295

climate forcing by BrC. Nevertheless, it should be noted that if mass absorption coefficients are

296

taken into account instead of oscillator strengths, the difference between biphenyls/terphenyls

297

and catechol should decrease due to the doubling and tripling of their molecular weights. Almost

298

all biphenyl and terphenyl derivatives present high wavelength maxima and now absorb in the

299

UVB and UVA regions. Such radiation is not filtered by the atmosphere, and so, can reach the

300

Earth’s surface and be absorbed by the biphenyl and terphenyl derivatives of catechol (leading to

301

climate forcing). Nevertheless, it should be noted that these compounds absorb only in the UV-

302

visible region. However, some authors have reported moderately and strongly absorption BrC

303

absorption cross sections at 350, 450, 550 and 650 nm.5 Thus, the absorption properties of these

304

individual oxidation products indicate that their contribution to BrC absorption should be limited

305

the region near 350 nm.


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 28

306

The increase in absorption wavelength and intensity (for biphenyl and terphenyl compounds)

307

results from π-conjugation formed between the different rings of these molecules. The π-

308

conjugation is formed due to the electron delocalization and orbital overlap that occur during the

309

coupling of semiquinone catechol radicals, which generate the biphenyl and terphenyl

310

derivatives. It is for this reason that polyhydroxylated single-ring catechol derivatives present

311

similar absorption wavelengths and intensities to the parent compound, regardless of the degree

312

of hydroxylation. Table 4 - Atomic Mulliken charge for the phenyl moeities of three catechol derivatives (Figure 2) at the PW91PW91/6-31+G(d,p) level of theory, in aqueous phase. The value for the gas phase are within parenthesis. Molecule

Moiety A

Moiety B


0.218 (-0.253)

-0.218 (0.253)

Biphenyl-2,3,3’,4’,4,5’-hexaol

-0.022 (0.095)

0.022 (-0.095)

Terphenyl-2’,3,3’,3’’,4,4’’-hexaol

-0.109 (-0.204)

-0.727 (-0.666)

Moiety C

0.836 (0.870)

313 314

Finally, the absorption intensity of all compounds is significantly higher in the aqueous phase

315

than in the gas phase. Thus, these compounds should have a more important role in climate

316

forcing when present in wet aerosols. The explanation can be found in different degrees of

317

delocalization of electron density in different environments, for the same molecule. It is known

318

that hyperchromism (increase in molar absorptivity) can result from higher electron


20

Page 21 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


319

delocalization. Thus, we have calculated the atomic Mulliken charges for the rings of three

320

different catechol derivatives (Table 4), in both aqueous phase and in vacuo. We can see that the

321

charge difference between the two rings of the biphenyl moieties is smaller in aqueous phase

322

than in the gas phase. This means that the charge density is more evenly distributed in condensed

323

phase, leading to higher electron delocalization in this solvent. A similar justification is seen for

324

the terphenyl molecule, as the charge difference between negatively and positively charged

325

moieties is smaller in aqueous phase (-1.672e) than in the gas phase (-1.740e), thereby indicating

326

a higher degree of electron delocalization in condensed phase.

327 328

ASSOCIATED CONTENT

329

Supporting Information. The following files are available free of charge.

330

Cartesian coordinates of important molecules (PDF)

331

Corresponding Author

332

*[email protected].

333 334

ACKNOWLEDGMENT

335

This work was made in the framework of the project Sustainable Advanced Materials (NORTE-

336

01-0145-FEDER-000028), funded by FEDER through “Programa Operacional do Norte

337

(NORTE2020)”. Acknowledgment to project POCI-01-0145-FEDER-006980, funded by

338

FEDER through COMPETE2020, is also made. L. Pinto da Silva acknowledges the Post-

339

Doctoral grant funded by project NORTE-01-0145-FEDER-000028. The Laboratory for


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

340

Computational Modeling of Environmental Pollutants-Human Interactions (LACOMEPHI) is

341

acknowledged.

Page 22 of 28

342 343

REFERENCES

344

1. Chen, Q.; Ikemori, F.; Mochida, M. Light Absorption and Excitation-Emission Fluorescence

345

of Urban Organic Aerosol Components and Their Relationship to Chemical Structure. Environ.

346

Sci. Technol. 2016, 50, 10859.

347

2. Liu, J.; Lin, P.; Laskin, A.; Laskin, J.; Kathmann, S.M.; Wise, M.; Caylor, R.; Imholt, F.;

348

Selimovic, V.; Shilling, J.E. Optical properties and aging of light-absorbing secondary organic

349

aerosol. Atmos. Chem. Phys. 2016, 16, 12815-12827.

350

3. Lin, P.; Liu, J; Shilling, J.E.; Kathmann, S.M.; Laskin, J.; Laskin, A. Molecular

351

characterization of brown carbon (BrC) chromophores in secondary organic aerosol generated

352

from photo-oxidation of toluene. Phys. Chem. Chem. Phys. 2015, 17, 23312-23325.

353

4. Andreae, M.O.; Gelencsér, A. Black carbon or brown carbon? The nature of light-absorbing

354

carbonaceous aerosols. Atmos. Chem. Phys. 2006, 6, 3131-3148.

355

5. Feng, Y.; Ramanathan, V.; Kotamarthi, V.R. Brown carbon: a significant atmospheric

356

absorber of solar radiation? Atmos. Chem. Phys. 2013, 13, 8607-8621.

357

6. Moise, T.; Flores, J.M.; Rudich, Y. Optical properties of secondary organic aerosols and their

358

changes by chemical processes. Chem. Rev. 2015, 115, 4400-4439.

359

7. Bond, T.C.; Zarzycki, C.; Flanner, M.G.; Koch, D.M. Quantifying immediate radiative forcing

360

by black carbon and organic matter with the Specific Forcing Pulse. Atmos. Chem. Phys. 2011,

361

11, 1505-1525.


22

Page 23 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


362

8. Ma, X.; Yu, F.; Luo, G. Aerosol direct radiative forcing based on GEOS-Chem-APM and

363

uncertainties. Atmos. Chem. Phys. 2012, 12, 5563-5581.

364

9. Chung, C.E.; Ramanathan, V.; Decremer, D. Observationally constrained estimates of

365

carbonaceous aerosol radiative forcing. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 11624-11629.

366

10. Frka, S.; Sala, M.; Kroflic, A.; Hus, M.; Cusak, A.; Grgic, I. Quantum Chemical Calculations

367

Resolved Identification of Methylnitrocatechols in Atmospheric Aerosols. Environ. Sci. Technol.

368

2016, 50, 5526-5535.

369

11. Lin, P.; Aiona, P.K.; Li, Y.; Shiraiwa, M.; Laskin, J.; Nizkorodov, S.A.; Laskin, A.

370

Molecular Characterization of Brown Carbon in Biomass Burning Aerosol Particles. Environ.

371

Sci. Technol. 2016, 50, 11815-11824.

372

12. Laskin, A.; Laskin, J.; Nizkorodov, S.A. Chemistry of Atmospheric Brown Carbon. Chem.

373

Rev. 2015, 115, 4335-4382.

374

13. Ramanathan, V.; Ramana, M.V.; Roberts, G.; Kim, D.; Corrigan, C.; Chung, C.; Winker, D.

375

Warming trends in Asia amplified by brown cloud solar absorption. Nature 2007, 448, 575-578.

376

14. Lin, G.X.; Penner, J.E.; Flanner, M.G.; Sillman, S.; Xu, L.; Zhou, C. Radiative forcing of

377

organic aerosol in the atmosphere and on snow: Effects of SOA and brown carbon. J. Geophys.

378

Res-Atmos 2014, 119, 7453-7476.

379

15. Cubasch, U.; Wuebbles, D.; Chen, D.; Facchini, M.C.; Frame, D.; Mahowald, N.; Winther,

380

J.-G. Introduction. In Climate Change 2013: The Physical Science Basis. Contribution of

381

Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate

382

Change; Cambridge University Press: Cambridge/New York, 2013.


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 28

383

16. Saleh, R.; Marks, M.; Heo, J.; Adams, P.J.; Donahue, N.M.; Robinson, A.L. Contribution of

384

brown carbon and lensing to the direct radiative effect of carbonaceous aerosols from biomass

385

and biofuel burning emissions. J. Geophys. Res. 2015, 120, 10285-10296.

386

17. Bahadur, R.; Praveen, P.S.; Xu, Y.Y.; Ramanathan, V. Solar absorption by elemental and

387

brown carbon determined from spectral observations. Proc. Natl. Acad. Sci. U.S.A. 2012, 109,

388

17366-17371.

389

18. Lambe, A.T.; Cappa, C.D.; Massoli, P.; Onasch, T.B.; Forestieri, S.D.; Martin, A.T.;

390

Cumming, M.J.; Croasdale, D.R.; Brune, W.H.; Worsnop, D.R.; Davidovits, P. Relationship

391

between oxidation level and optical properties of secondary organic aerosol. Environ. Sci.

392

Technol. 2013, 47, 6349-6357.

393

19. Lee, H.J.; Aiona, P.K.; Laskin, A.; Laskin, J.; Nizkorodov, S.A. Effect of solar radiation on

394

the optical properties and molecular composition of laboratory proxies of atmospheric brown

395

carbon. Environ. Sci. Technol. 2014, 48, 10217-10226.

396

20. Lee, A.K.Y.; Zhao, R.; Li, R.; Liggio, J.; Li, S.M.; Abbatt, J.P.D. Formation of light

397

absorbing organo-nitrogen species from evaporation of droplets containing glyoxal and

398

ammonium sulfate. Environ. Sci. Technol. 2013, 47, 12819-12826.

399

21. Alexander, D.T.L.; Crozier, P.A.; Anderson, J.R. Brown carbon spheres in East Asian

400

outflow and their optical properties. Science 2008, 321, 833-836.

401

22. Bond, T.C.; Bergstrom, R.W. Light absorption by carbonaceous particles: An investigative

402

review. Aerosol Sci. Technol. 2006, 40, 27-67.

403

23. Veres, P.; Roberts, J.M.; Burling, I.R.; Warneke, C.; de Gouw, J.; Yokelson, R.J.

404

Measurements of gas-phase inorganic and organic acids from biomass fires by negative-ion

405

proton-transfer chemical-ionization mass spectrometry. J. Geophys. Res. 2010, 115, D23302.


24

Page 25 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


406

24. Adounkpe, J.; Aina, M.; Mama, D.; Sinsin, B. Gas chromatography mass spectrometry

407

identification of labile radicals formed during pyrolysis of catechol, hydroquinone, and phenol,

408

through neutral pyrolysis product mass analysis. ISRN Environ. Chem. 2013, 2013, 1.

409

25. Desyaterik, Y.; Sun,Y.; Shen, X.; Lee, T.; Wang, X.; Wang, T.; Collett, J.L. Speciation of

410

“brown” carbon in cloud water impacted by agricultural biomass burning in eastern China. J.

411

Geophys. Res.-Atmos. 2013, 118, 7389-7399.

412

26. Pillar, E.A.; Zhou, R.; Guzman, M.I. Heterogeneous Oxidation of Catechol. J. Phys. Chem. A

413

2015, 119, 10349-10359.

414

27. Zein, A.E.; Coeur, C.; Obeid, E.; Lauraguais, A.; Fagniez, T. Reaction kinetics of catechol

415

(1,2-benzenediol) and guaiacol (2-methoxyphenol) with ozone. J. Phys. Chem A 2015, 119,

416

6759-6765.

417

28. Pillar, E.A.; Camm, R.C.; Guzman, M.I. Catechol oxidation by ozone and hydroxyl radicals

418

at the air-water interface. Environ. Sci. Technol. 2014, 48, 14352-14360.

419

29. Frka, S.; Sala, M.; Kroflic, A.; Hus, M.; Cusak, Grgic, I. Quantum Chemical Calculations

420

Resolved Identification of Methylnitrocatechols in Atmospheric Aerosols. Environ. Sci. Technol.

421

2016, 50, 5526-5535.

422

30. Fu, Z.; Wang, Y.; Chen, J.; Wang, Z.; Wang, X. How PBDEs Are Transformed into

423

Dihydroxylated and Dioxin Metabolites Catalyzed by the Active Center of Cytochrome P450s: A

424

DFT Study. Environ. Sci. Technol. 2016, 50, 8155-8163.

425

31. Krzeminska, A.; Paneth, P. DFT Studies of SN2 Dechlorination of Polychlorinated

426

Biphenyls. Environ. Sci. Technol. 2016, 50, 6293-6298.

427

32. Zheng, Q.; Durkin, D.P.; Elenewski, J.E.; Sun, Y.; Banek, N.A.; Hua, L.; Chen, H.; Wagner,

428

M.J.; Zhang, W.; Shuai, D. Visible-Light-Responsive Graphitic Carbon Nitride: Rational Design


25


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 28

429

and Photocatalytic Applications for Water Treatment. Environ. Sci. Technol. 2016, 50, 12938-

430

12948.

431

33. Pinto da Silva, L.; Ferreira, P.J.O.; Duarte, D.J.R.; Miranda, M.S.; Esteves da Silva, J.C.G.

432

Structural, Energetic, and UV-Vis Spectral Analysis of UVA Filter 4-tert-Butyl-4´-

433

methoxydibenzoylmethane. J. Phys. Chem. A 2014, 118, 1511-1518.

434

34. Pinto da Silva, L.; Ferreira, P.J.O.; Miranda, M.S.; Esteves da Silva, J.C.G. A theoretical

435

study of the UV absorption of 4-methylbenzylidene camphor: from the UVB to the UVA region.

436

Photochem. Photobiol. Sci. 2015, 14, 465-472.

437

35. Gaussian 09, Revision A.02, M.J. Frisch et al, Gaussian, Inc., Wallingford CT, 2009.

438

36. Adamo, C.; Barone, V. Toward reliable density functional methods without adjustable

439

parameters: The PBE0 model. J. Chem. Phys. 1999, 110, 6158-6170.

440

37. Pinto da Silva, L.; Esteves da Silva, J.C.G. Analysis of the Performance of DFT Functionals

441

in the Study of Light Emission by Oxyluciferin Analogs. Int. J. Quantum Chem. 2013, 113, 45-

442

51.

443

38. Jacquemin, D.; Perpète, E.A.; Ciofini, I.; Adamo, C. Assessment of the ωB97 family for

444

excited-state calculations. Theor. Chem. Acc. 2011, 128, 127-136.

445

39. Jacquemin, D.; Wathelet, V.; Perpète, E.A.; Adamo, C. Extensive TD-DFT Benchmark:

446

Singlet-Excited States of Organic Molecules. J. Chem. Theory Comput. 2009, 5, 2420-2435.

447

40. Perdew, J.P.; Chevary, J.A.; Vosko, S.H.; Jackson, K.A.; Pederson, M.R.; Singh, D.J.;

448

Fiolhais, C. Atoms, molecules, solids, and surfaces: Applications of the generalized gradient

449

approximation for exchange and correlation. Phys. Rev. B Condens. Matter 1992, 46, 6671-6687.

450

41. Scalmani, G.; Frisch, M.J.; Mennucci, B.; Tomasi, J.; Cammi, R.; Barone, V. Geometries and

451

properties of excited states in the gas phase and in solution: Theory and application of a time-


26

Page 27 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


452

dependent density functional theory polarizable continuum model. J. Chem. Phys. 2006, 124,

453

094107.

454

42. King, G.A.; Oliver, T.A.A.; Dixon, R.N.; Ashford, M.N.R. Vibrational energy redistribution

455

in catechol during ultraviolet photolysis. Phys. Chem. Chem. Phys. 2012, 14, 3338-3345.

456

43. Anouar, E.H.; Gierschner, J.; Duroux, J.L.; Trouillas, P. UV/Visible spectra of natural

457

polyphenols: A time-dependent density functional theory study. Food Chem. 2012, 131, 79-89.

458

44. Scalmani, G.; Frisch, M.J. Continuous surface charge polarizable continuum models of

459

solvation. I. General formalism. J. Chem. Phys. 2010, 132, 114110.

460

45. Lu, T.; Chen, F. Multiwfn: A multifunctional wavefunction analyzer. J. Comput. Chem.

461

2012, 33, 580-592.

462

46. Bruhn, T.; Schaumloffel, A.; Hemberger, Y.; Bringmann, G. SpecDis: Quantifying the

463

Comparison of Calculated and Experimental Electronic Circular Dichroism Spectra. Chirality

464

2013, 25, 243-249.

465

47. Ofner, J.; Kruger, H.U.; Grothe, H.; Schmitt-Kopplin, P.; Whitmore, K.; Zetzsch, C. Physico-

466

chemical characterization of SOA derived from catechol and guaiacol - a model substance for the

467

aromatic fraction of atmospheric HULIS. Atmos. Chem. Phys. 2011, 11, 1-15.

468

48. Phillips, S.M.; Smith, G.D. Light Absorption by Charge Transfer Complexes in Brown

469

Carbon Aerosols. Environ. Sci. Technol. Lett. 2014, 1, 382-386.

470

49. Barnum, T.J.; Medeiros, N.; Hinrichs, R.Z. Condensed-phase versus gas-phase ozonolysis of

471

catechol: A combined experimental and theoretical study. Atmos. Environ. 2012, 55, 98-106.

472

50. Miranda, M.S.; Pinto da Silva, L.; Esteves da Silva, J.C.G. UV filter 2-ethylhexyl 4-

473

methoxycinnamate: a structure, energetic and UV-vis spectral analysis based on density

474

functional theory. J. Phys. Org. Chem. 2014, 27, 47-56.


27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 28

475

51. Pinto da Silva, L.; Esteves da Silva, J.C.G. Theoretical fingerprinting of the photophysical

476

properties of four firefly bioluminophores. Photochem. Photobiol. Sci. 2013, 12, 2028-2035.

477

52. Cai, D.; Marques, M.A.L.; Milne, B.F.; Nogueira, F. Bioheterojunction Effect on

478

Fluorescence Origin and Efficiency Improvement of Firefly Chromophores. J. Phys. Chem. Lett.

479

2010, 1, 2781-2787.

480 481 482


28

DFT Calculation of the Absorption Properties of Brown Carbon

Recommend Documents