Molecular Modeling Studies of the Structural, Electronic, and UV

Article pubs.acs.org/JPCA

Molecular Modeling Studies of the Structural, Electronic, and UV Absorption Properties of Benzophenone Derivatives Bianca A. M. Corrêa, Arlan S. Gonçalves,† Alessandra M. T. de Souza, Caroline A. Freitas, Lúcio M. Cabral,‡ Magaly G. Albuquerque,⊥ Helena C. Castro,# Elisabete P. dos Santos,§ and Carlos R. Rodrigues* CCS, Faculty of Pharmacy, ModMolQSAR, Federal University of Rio de Janeiro (UFRJ), 21941-590 Rio de Janeiro, RJ, Brazil S Supporting Information *

ABSTRACT: Benzophenone derivatives (BZP), an important class of organic UV filters, are widely used in sunscreen products due to their ability to absorb in the UVA and UVB ranges. The structural, electronic, and spectral properties of BZP derivatives have been studied by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. DFT/B3LYP with the 6-31G(d) basis set is an accurate method for optimizing the geometry of BZPs. The absorption maxima obtained from the TD-DFT calculations in a vacuum were in agreement with the experimental absorption bands and showed that the main electronic transitions in the UVA/UVB range present π → π* character, the major transition being HOMO → LUMO. The oscillator strength seems to increase in the presence of disubstitution at the para position. For protic substituents, the position appears to be related to the absorption band. Absorption in the UVB range occurs in the presence of para substitution, whereas ortho substitution leads to absorption in the UVA spectral region. The obtained results provide some features for BZP derivatives that can be useful for customizing absorption properties (wavelengths and intensities) and designing new BZP derivatives as sunscreens.

1. INTRODUCTION

Some BZPs have been approved by regulatory agencies in many countries for use in sunscreens, including 2-hydroxy-4methoxybenzophenone (oxybenzone or benzophenone-3; BZP-3), 2,2-hydroxy-4-methoxybenzophenone (dioxybenzone or BZP-8), 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (sulisobenzone or BZP-4), and diethylamino hydroxybenzoyl hexyl benzoate (DHHB).7,8 BZP-3 is one of the most widely used UV filters in commercial sunscreens due to its ability to absorb in the UVB and UVA regions of the electromagnetic spectrum, although it has poor UVA efficiency.7,8 DHHB is a new UV filter with good photostability and a UVA absorption spectrum peak at 354 nm.8 Molecular modeling is an important and useful tool that allows a better understanding of spectral behavior.7,9 It helps to establish the structure−property relationships9 and also enables the screening of compounds that have the ability to absorb radiation in the desired range.7,9,10 Furthermore, it allows for the prediction and interpretation of the excited-state properties of different types of molecules.9−14 Density functional theory (DFT) is a quantum mechanical method that can provide an accurate description of the structure, energy, and molecular properties of the ground state. By extending the efficiency of the DFT calculations to excited

The electromagnetic spectrum emitted by the sun includes ultraviolet (UV) radiation that is comprosed of UVA, UVB, and UVC radiation.1 The human body is constantly exposed to the UVB (∼290−320 nm) and UVA (320−400 nm) wavelengths.2,3 The UVB wavelengths less than 295 nm and the UVC radiation are filtered by the stratospheric ozone layer.4 Acute and chronic exposure to solar UV radiation causes skin damage, including erythema (sunburn), cutaneous photoaging, immune suppression, and an increased risk of skin cancer. Organic UV filters are the most common active constituents in sunscreen products used for attenuating skin photodamage.1,4,5 Organic filters absorb UV radiation by exciting an electron from its ground state into an excited state due to the presence of a system with certain unsaturated groups (π orbitals) and atoms with unpaired electrons (n orbitals). Some saturated groups that bond to this system also contribute to UV absorption. Benzophenone derivatives (BZP), an important class of organic UV filters, are widely used in sunscreen products due to their ability to absorb in the UVA and UVB ranges. BZPs (i.e., diphenylketones) usually show n → π* and π → π* transitions, resulting in two peaks in the UV range, one in the UVA range and another in the UVB range.6 Some peaks in the UV region have also been attributed to the intramolecular charge-transfer transition involving the carbonyl and hydroxyl groups of certain hydroxyBZPs (o-hydroxybenzophenones).6,7 © 2012 American Chemical Society

Received: June 21, 2012 Revised: August 29, 2012 Published: August 30, 2012 10927

dx.doi.org/10.1021/jp306130y | J. Phys. Chem. A 2012, 116, 10927−10933

The Journal of Physical Chemistry A

Article

The semiempirical and ab initio methods underestimate the OC(2) bond length. Larger OC(2) bond length variations were observed between experimental25 and HF/6-31G(d) or HF/6-31G(d,p) results (Δrmax = 0.043 Å for both). There is an intramolecular hydrogen bond between the hydroxyl group and the carboxyl oxygen that influences the OC(2) bond length. The smaller the hydrogen bond length, the longer the OC(2) length.26 The semiempirical and ab initio methods showed smaller OC(2) and longer O− H···OC(2) bond lengths than those obtained by experimental and DFT/B3LYP methods. The bond lengths calculated using the DFT/B3LYP method with 6-31G(d), 6-31G(d,p), and 6-31+G(d) basis sets are in agreement with the experimental results25 (Δrmax < 0.02 Å). The difference value percentages (DVPs) between the calculated parameters by the DFT/B3LYP method with the 6-31G(d), 6-31G(d,p), and 6-31+G(d) basis sets and experimental data25 are shown in the Supporting Information. It can be observed that all of the DVP values are less than 2.0%. Considering the valuable accuracy and computational speed9 of the most parsimonious basis set, the DFT/B3LYP/6-31G(d) method was chosen for the following calculations. Additionally, other optimized structures of BZPs have been compared to X-ray crystal structures available in the CSD,25,27−35 and all DVP values are less than or close to 2.0% (see the Supporting Information). The structural parameters calculated with the DFT/B3LYP/6-31G(d) method and those that were obtained experimentally are reported with the respective DVP values in the Supporting Information. 3.2. Electronic and UV Absorption Properties of BZPs. 3.2.1. Methodology Validation. To determine the ability to predict UVA/UVB absorption spectra, TD-DFT calculations in vacuum were performed on the selected optimized geometry of BZP-3 at the same level of theory as that used for the optimization, and the results were compared with an experimental absorption spectrum measured in a dichloromethane solution (20 μg/mL of BZP-3) (Figure 1). For clarity,

states, the time-dependent density functional theory (TDDFT) allows good agreement between calculated and experimental spectra.9,15−17 This investigation focuses on BZP derivatives and presents molecular modeling studies of the structural, electronic, and UV spectral properties of BZP derivatives that have been approved or that have substituents similar to those that have been approved by regulatory agencies. To reach these goals, in the present work, we performed quantum mechanical calculations of the ground and excited states of BZP derivatives using the DFT and TD-DFT15,16 methods. In the first step, the methodology to be used for the geometry optimizations was set up by comparing the geometric parameters of the calculated structure and crystal data from the Cambridge Structural Database (CSD).18 In the second step, the electronic and UV spectral properties were calculated. To evaluate the predictive capacity (i.e., accuracy) of the method, some of the results were compared with experimental data. Lastly, the results were analyzed, and the structure−property relationships of BZP derivatives were established to obtain data that may be useful for customizing the absorption properties (wavelengths and intensities) and designing new BZP derivatives as sunscreens.

2. METHODOLOGY 2.1. Theoretical Calculations. Molecular structures were built, and the geometries were optimized using the Spartan’10 program (Wavefunction Inc., Irvine, California, U.S.A.). Preliminary calculations with semiempirical RM1 and PM6, ab initio HF, and DFT with the hybrid functional B3LYP (Becke’s hybrid exchange functional B319 with the Lee−Yang− Parr correlation functional LYP20,21) using different basis sets were performed on BZP-3 to establish the methodology to be used to optimize the geometry of the compounds. The optimized structures have been statistically analyzed using the crystal data from BZP derivatives available in CSD, and all results are reported in the Supporting Information. Subsequently, Cartesian coordinates based on the bond lengths and angles of the optimized structures of BZP derivatives were used as inputs for theoretical studies of absorption spectra by means of TD-DFT15,16,22 at the same level of theory as B3LYP/6-31G(d) in vacuum using the GAMESS US23,24 program. The lowest 10 singlet−singlet excitations have been computed with their respective wavelengths, transition energies, main transition configurations, and oscillator strengths. 2.2. Experimental Section. Absorbance spectra of BZP-3 were analyzed at room temperature (297 K) on a UV/vis spectrophotometer (JASCO V-630). The data were corrected for solvent background by the instrument’s calibration using the solvent as a blank. The spectrum in the range of 270−400 nm was measured in a solution (20 μg/mL) of BZP-3 (Aldrich, 98% pure) that was prepared in a dichloromethane solvent (Sigma-Aldrich, ≥99.8% pure).

Figure 1. Comparison of the BZP-3 experimental UV absorption (dichloromethane) and the theoretical UV absorption maxima (vacuum, TD-DFT/B3LYP/6-31G(d) method). The normalization of the absorbance was performed according to the maximum intensity of each spectrum.

3. RESULTS AND DISCUSSION 3.1. Ground-State Geometry Optimization. The optimized and experimental (available X-ray crystal structure25) geometric parameters of BZP-3 are reported in the Supporting Information. The optimized geometries are local minimumenergy structures obtained by semiempirical RM1 and PM6, ab initio HF, and DFT/B3LYP methods in the ground state.

the maximum absorbance was normalized according to the maximum intensity of each spectrum. The experimental absorption bands measured at 287 and 325 nm were computed at 285 and 326 nm in a vacuum. Therefore, the absorption maxima computed in a vacuum are in agreement with the experimental absorption bands. 10928



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Table 1. Transitions (nm/eV), Oscillator Strength ( f) ( f > 0.1), and Composition in Terms of the MOs Calculated for the BZPs

Previous studies indicated that the absorption spectra of BZP-3 are not strongly affected by the presence of the solvent.7 However, other BZPs show solvatochromic shifts in different solvents.6,7 Although solvatochromic effects in the spectral properties are important to quantitative simulations, calculations of absorption spectra with molecules in vacuum can provide qualitative trends.9 3.2.2. Structure−Property Relationships. In an effort to determine the structure−property relationships, the TDDFT/ B3LYP/6-31G(d) calculations of the absorption spectra in a vacuum were carried out using the optimized geometry of BZP derivatives that have been approved or with substituents similar to those that have been approved by regulatory agencies. The most relevant wavelengths (λ > 280 nm), the energy of transition and the oscillator strengths (f > 0.1) calculated from the absorption spectra, and their main transition configurations are listed in Table 1. To confirm the accuracy of the TD-DFT calculations in a vacuum, experimental UV absorption spectra available in previous reports were used.6,7 The experimental UV absorption spectra are in agreement with the TD-DFT calculations performed on the isolated BZP derivatives (R2 = 0.9912) (Figure 2). The nonsubstituted BZP shows an experimental band at 257 nm in water.6 This band was calculated in a vacuum at 261 nm. The 2,2′-hydroxy-4-methoxybenzophenone experimental absorption bands measured at 299 and 355 nm in toluene7 were computed at 296 and 356 nm in a vacuum. The compound 4-hydroxybenzophenone shows an experimental band at 285 nm in diethyl ether6 and a theoretical absorption maximum in a vacuum at 283 nm. The experimental absorption maxima measured at 261 and 337 nm in ethanol6 were calculated in a vacuum at 268 and 340 nm for 2hydroxybenzophenone. The 2,4-hydroxybenzophenone experimental UV absorptions at 281 and 324 nm in cyclohexane6 were calculated at 281 and 323 nm in a vacuum. a. Oxygenated BZP Derivatives. A general analysis of hydroxybenzophenone absorption shows that these derivatives exhibit at least one peak in the UVA or UVB range, while 2,4OHBZP, 2,4,4′-OHBZP, and 2,2′,4,4′-OHBZP show maximum wavelengths in both spectra regions. Considering the nature of the molecular orbitals involved in the transitions, all derivatives showed absorptions maximum peaks assigned to a π → π* character (Figure 3). For monohydroxybenzophenones (2-OHBZP and 4OHBZP), the lower-energy transition is predominantly HOMO → LUMO (Table 1) and shifts with changes in the hydroxyl group position (Figure 3). This transition corresponds to 340 nm (f = 0.104) for 2-OHBZP and 283 nm (f = 0.280) for 4-OHBZP. Considering the molecular orbital distribution for both derivatives, the HOMO is mainly localized in the substituted ring A (Figure 3). Furthermore, the orbital transition of 2-OHBZP is accompanied by a change in the electron density on the hydroxyl and carbonyl oxygens attributed to an excited-state proton transfer (ESPT), as already reported in previous studies.6,7 Addition of another hydroxyl substituent at the ortho position led to some red shifting in the UVA energy transitions, 340 to 364 nm (2-OH/2,2′-OH) and 283 to 323 nm (4-OH/ 2,4′-OH), with the same HOMO → LUMO transition accompanied by a change in the electron density on the hydroxyl and carbonyl groups assigned to a proton transfer in the excitation process. We can infer that the proximity of the hydroxyl and carbonyl groups promotes lower-energy tran-

λ/ nm

eV

MO

f

2-OH 4-OH 2,2′−OH 2,4-OH

340 283 364 281

3.651 4.375 3.409 4.407

0.104 0.280 0.181 0.226

4,4′−OH

323 287

3.847 4.323

2,4,4′−OH

289

4.291

367

3.383

2,2′,4,4′−OH

295

4.210

4-MeO 4,4′-MeO

346 291 283

3.588 4.271 4.387

285

4.358

326 296

3.812 4.188

356

3.486

297

4.181

351

3.536

4-EtO

283

4.376

4,4′-EtO

293

4.239

2-OH, 4-EtO

286

4.341

326

3.803

2-NH2

361

3.431

4-NH2

304

4.082

4,4′-NH2

307

4.043

2-OH, 4-NH2

297

4.175

310

3.997

4-N(Me)2

311

3.990

4,4′-N(Me)2

307

4.043

2-OH,4-N(Me)2

322

3.855

4-N(Et)2 4,4′-N(Et)2

323 335

3.839 3.710

2-OH,4-N(Et)2

325

3.814

HOMO → LUMO: 0.92 HOMO → LUMO: 0.78 HOMO → LUMO: 0.94 HOMO−3 → LUMO: −0.85 HOMO → LUMO: 0.83 HOMO−1 → LUMO: 0.94 HOMO−1 → LUMO: 0.63 HOMO−2 → LUMO: −0.59 HOMO → LUMO: −0.83 HOMO−2 → LUMO: −0.93 HOMO → LUMO: 0.92 HOMO → LUMO: 0.81 HOMO−1 → LUMO: −0.95 HOMO−1 → LUMO: −0.86 HOMO → LUMO: 0.87 HOMO−2 → LUMO: 0.84 HOMO → LUMO: −0.92 HOMO−2 → LUMO: −0.94 HOMO → LUMO: −0.93 HOMO → LUMO: 0.757 HOMO−1 → LUMO: 0.94 HOMO−1 → LUMO: 0.870 HOMO → LUMO: 0.874 HOMO → LUMO: −0.919 HOMO → LUMO: −0.86 HOMO → LUMO: −0.93 HOMO−1 → LUMO: −0.770 HOMO → LUMO: −0.704 HOMO → LUMO: −0.84 HOMO → LUMO: 0.949 HOMO → LUMO: −0.873 HOMO → LUMO 0.761 HOMO → LUMO: 0.949 HOMO → LUMO: 0.910

Subst-BZP

2-OH, 4-MeO (BZP3) 2,2′−OH, 4-MeO (BZP-8)

2,2′−OH, 4,4-MeO

0.144 0.412 0.210

0.228 0.167 0.348 0.291 0.425 0.235 0.179 0.186 0.263 0.188 0.436 0.236 0.511 0.244 0.186 0.114 0.272 0.496 0.118 0.199 0.250 0.496 0.366 0.237 0.712 0.414

sitions. With the addition of an extra hydroxyl group at the para position, the 4,4′-OHBZP derivative showed larger oscillator strength than the monosubstituted derivative (Table 1). In this molecule, the transition is predominantly HOMO−1 → 10929



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Ortho and para hydroxylation of BZP (2,4,4′-OHBZP and 2,2′,4,4′-OHBZP) led to a broad absorption spectrum (Table 1). However, these compounds can be absorbed through human skin after dermal application and are able to mimic the biological activities of hormones, showing estrogenic or antiandrogenic activity.36−38 The endocrine-disrupting actions of BZPs may pose a risk to humans and wildlife, a nondesirable feature for sunscreen products.36 Substitution of a methoxy at the ortho position (2MeOBZP) led to an absorption peak at 266 nm, which is out of the desirable range. In contrast, substitution of a methoxy at the para position (4-MeOBZP) resulted in an absorption maximum in the UVB range at 291 nm with a transition assigned to HOMO → LUMO, as seen for 4-OHBZP. This electronic transition involves the substituted ring A, its substituent, and the carbonyl group (Table 1 and Figure 3). Surprisingly, the addition of an extra methoxy at the para position of ring B (4,4′-MeOBZP) led to a slight blue shift in the UVB region, with an already expected increase of oscillator strength (Table 1). The presence of a hydroxyl substituent at the ortho position led to an extra absorption in the UVA region of 4-MeOBZP (2-

Figure 2. Comparison between the theoretical and experimental wavelengths (nm) of the absorption maxima.

LUMO, where HOMO−1 is localized in both ring moieties, most likely due to the presence of hydroxyl substituents (Figure 3). This disubstitution at the para position leads to highintensity absorption in the UVB region in comparison with monosubstitution at this position.

Figure 3. Frontier molecular orbitals of oxygenated BZP derivatives. 10930



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Figure 4. Frontier molecular orbitals of aminobenzophenones.

OH-4-MeOBZP, 2,2′-OH-4-MeOBZP) and 4,4′-MeOBZP (2,2′-OH-4,4′-MeOBZP), categorizing these derivatives as broad-spectrum organic filters. However, studies showed that these para methoxylated derivatives can also be absorbed through the skin and undergo biotransformation by demethylation, leading to metabolites with estrogenic activity.36,37,39 In all cases, it can be seen that the occupied orbital contribution (HOMO and HOMO−1) for UVA and UVB absorption is predominantly related to the methoxy and its substituted ring (Figure 3). Ethoxybenzophenones showed the same pattern as the previous derivatives. Substitution at the ortho position, as with the methoxy group, did not result in absorption within the desirable spectral range. Para substitution seems to be related to UVB absorption as well as the hydroxylation of the 4-EtOBZP derivative (2-OH-4-EtOBZP), which broadened the absorption spectrum, but with a lower oscillator strength (Table 1). Considering all of the oxygen-substituted BZP derivatives, 4,4′-EtOBZP exhibits the largest oscillator strength (f = 0.511), with λmax computed at 294 nm and a HOMO−1 → LUMO transition involving the electron density on the oxygen of the ethoxy group and both substituted rings (Table 1 and Figure 3). b. Aminobenzophenones. Similar transition energies and oscillation strengths for the amino and hydroxyl-substituted BZPs were expected due to their electronic resemblances (Table 1). We may infer that the presence of OH and NH at the ortho position is accompanied by a change in the electron density on the OH/NH and carbonyl oxygen, which supports an ESPT and keto−enol/amino−imino tautomerism. Comparison between OH/NH and O-alkyl/N-dialkyl substituents at the ortho position confirms that the low energy necessary for absorption in the UVA region is related to this proton transfer. The λmax

computed for 2-N(Me)2BZP and 2-N(Et)2BZP are out of the desired range (lower than 260 nm). The same was observed for alkoxy groups at the ortho position, as already reported in the present study. In the case of the para amino-substituted BZPs, the disubstitution increases the oscillator strength similarly to hydroxyl-substituted BZPs (Table 1). Furthermore, ortho hydroxylation also broadened the absorption spectrum, with the λmax computed at 297 and 310 nm assigned to HOMO−1 → LUMO and HOMO → LUMO transitions, respectively. Differing from the oxygen-substituted BZPs, hydroxylation of 4-NH2BZP at the ortho position (2-OH-4-NH2BZP) did not induce an absorption peak in the UVA range, leading only to an extra absorption in the UVB range (Table 1). These absorptions showed the coefficient of distribution of the occupied orbitals, HOMO and HOMO−1, mainly localized in the substituted A ring and its substituents due to their inductive effect (Figure 3). The presence of alkylamino substituents (-N(Me)2 and -N(Et)2) at the para position led to a red shift from 311 nm for 4-N(Et)2BZP to 330 nm for 4,4′-N(Et)2BZP, and a smaller red shift was observed from 323 nm for 4-N(Me)2 to 334 nm for 4,4′-N(Me)2BZP.The electronic transitions of these derivatives involve a HOMO → LUMO transition within the substituted ring and its substituents (Figure 4). Similarly to 4-NH2BZP, hydroxylation of alkylamino derivatives, 2-OH-4-N(Me)2BZP and 2-OH-4-N(Et)2BZP, did not induced a broad absorption spectrum and only led to a redshifted absorption spectrum. Due to this substitution, 2-OH-4N(Me)2BZP presented a red shift from the UVB to the UVA region (311/322 nm), showing a strong resonance effect related to the hydroxyl substituent. All diethylaminobenzophenone derivatives exhibit a single peak in the UVA region with a HOMO → LUMO transition 10931



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Present Addresses

involving the substituted rings. Interestingly, 4,4′-N(Et)2BZP showed the highest oscillator strength of all of the BZP derivatives studied. c. Other BZP Derivatives. The λmax values computed for 2COOH-, 2-COOMe-, and 2-COOEt-substituted BZPs are out of the desired range, exhibiting maximum absorptions lower than 280 nm.

†

Chemistry Department, Federal Institute of Education, Science and Technology (IFES), Guarapari, ES 29215-090, Brazil. ‡ CCS, Faculty of Pharmacy, LabTIF, Federal University of Rio de Janeiro (UFRJ), 21941-590 Rio de Janeiro, RJ, Brazil § CCS, Faculty of Pharmacy, LADEG, Federal University of Rio de Janeiro (UFRJ), 21941-590 Rio de Janeiro, RJ, Brazil. ⊥ IQ-CCMN, Department of Organic Chemistry, LabMMol, Federal University of Rio de Janeiro (UFRJ), 21949-900 Rio de Janeiro, RJ, Brazil. # Institute of Biology, LABioMol, Fluminense Federal University, 24001-970 Niteroi, RJ, Brazil.

4. CONCLUSION Here, we report on our studies of the structural, electronic, and spectral properties of BZP derivatives with different substituents and ring positions as UV absorbers. The DFT/B3LYP with the 6-31G(d) basis set proved to be an accurate method for optimization of the geometry of the BZPs. Using TD-DFT, we reproduced the experimental UV absorption wavelengths of a set of BZP derivatives and combined the data to establish their structure−property relationships. After validation of the computational methodology using experimental data from BZP-3, we performed geometry optimizations and calculations of the UV absorption spectra of BZP derivatives. Our results showed that the main electronic transitions in the UVA/UVB range present π → π* character, with HOMO → LUMO being the major transition. The occupied orbital involved in the transition (HOMO, HOMO−1, HOMO−2, and/or HOMO− 3) is normally distributed over the substituted ring, including the electron-donating substituent. The oscillator strength, which is related to the strength of the transition, seems to increase in the presence of disubstitution at the para position, with the exception of 4,4′-MeOBZP. The highest oscillator strength, f = 0.712, occurs for 4,4′N(Et2)BZP. In contrast, it seems that substitution at the ortho position is directly related to a lower oscillator strength and absorption in the UVA region. We can infer that the presence of protic substituents at this position decreases the energy necessary for the electronic transition because proximity to the BZP carbonyl results in tautomerism. Finally, the position of protic substituents on the BZP moiety appears to be related to the absorption peak; absorption in the UVB range occurs in the presence of para substitution, whereas ortho substitution leads to absorption in the UVA spectral region. Overall, our TD-DFT calculation results revealed some features of BZP derivatives that may be useful in further investigations of safer organic UV filters with broad absorption spectra.

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Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This study was supported by Coordenaçaõ de Aperfeicoamento ́ Superior (CAPES), Rede Nanobiotecde Pessoal de Nivel ́ Brasil, Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq), and Fundaçaõ de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ).

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ASSOCIATED CONTENT

S Supporting Information *

Difference value percentages (DVPs) between the calculated (DFT) and experimental geometries of BZP-3; list of the CSD refcodes and references for the statistically analyzed benzophenone derivatives; geometric parameters and H-bond length of BZP-3 calculated using different methods and demonstrated experimentally; and structural parameters of benzophenone derivatives calculated with DFT/B3LYP/6-31G(d) and demonstrated experimentally. This material is available free of charge via the Internet at http://pubs.acs.org.

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. 10932



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Molecular Modeling Studies of the Structural, Electronic, and UV

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