A DFT/TDDFT study of porphyrazines and phthalocyanine oxo‐titanium derivatives as potential dyes in solar cells

Density functional theory and time dependent density functional theory calculations at the level of LDA/BP86/TZ2P were performed systematically on several Ti(IV) complexes of porphyrazines and one phthalocyanine. We performed an analysis of the frontier molecular orbitals of the ground state electronic structures and also discuss in particular the good concordance of our results with the experimental data, which affords to predict the geometrical and optical properties of new complexes ( 3 , 4 , and 7 ). We also emphasize the characterization of the UV–vis absorption spectra and propose transitions that contribute to the Q and B bands. Some useful calculated properties in complexes 2 , 3 , and 7 , like: high light absorption in the visible region of the spectra, transitions involved in these bands with a determined direction, charge separation, bigger highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO‐LUMO) gaps than complexes 4 and 5 , and the energy of their LUMO orbitals (that are higher than the lowest energy level of the conduction band of the TiO₂) indicate that system complexes 2 , 3 , and 7 could act as light‐harvesting sensitizers for dye‐sensitized solar cells (DSCs). These proposals were made using a model of the previously experimentally known phthalocyanine, which was used as sensitizer in DSCs devices, comparing its electronic properties with the herein proposed sensitizers. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Assessment of PBE0 for evaluating the absorption spectra of carbonyl molecules

Using the parameter‐free PBE0 hybrid functional, we compute the UV/Vis spectra of a series of solvated compounds presenting a carbonyl chromophoric unit linked to a carbon–carbon double bond. It turns out that PBE0 is extremely efficient for accurately reproducing experimental values, with a mean unsigned error of 7 nm for an extended set of compounds, although no fitting or statistical treatments are performed. PBE0 has a predictive efficiency comparable to the well‐known Woodward–Fieser empirical formula, and can therefore be used to extend these rules without requiring additional experimental results. Consequently, the UV/Vis spectra of several compounds that have not yet been synthesized are predicted. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

A comparative DFT study of substrates and products of industrial enzyme nitrile hydratase

Nitrile hydratase (NHase) is a metalloenzyme used in industrial biotechnology for a large scale production of common chemicals. NHases convert nitriles to the corresponding amides. Although the structures of some forms of NHases containing nonheme low spin Fe(III) or low spin noncorrinoid Co(III) are known, neither a catalytic mechanism nor the reasons of high selectivity towards aromatic ligands are recognized. Optimized geometries, molecular electrostatic potential maps and infrared spectra of commercially important aromatic substrates of the NHase (nicotinonitrile, o‐, m‐, p‐methylbenzonitrile) and the corresponding products (nicotinamide, o‐, m‐, p‐methylbenzamid) were investigated using the density functional theory method with the B3LYP functional and the 6‐31G(d,p) basis set. Calculated hypothetical intrinsic reaction paths indicate that benzimidic acids may be involved as intermediates. This study elucidates differences in the electronic properties of substrates and products of NHases, provides an insight into the molecular basis of the catalytic reaction and helps to explain varying enzymatic activities of microbial NHases. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

B3LYP,BLYP and PBE DFT band structures of the nucleotide base stacks

DFT crystal orbital (band structure) calculations have been performed for the nucleotide base stacks of cytosine, thymine, adenine, and guanine arranged in DNA B geometry. The band structures obtained with PBE, BLYP, and B3LYP functionals are presented and compared to other related experimental and theoretical results. The influence of the quality of the basis set on the fundamental gap values was also investigated using Clementi's double ζ, 6‐31G and 6‐31G* basis sets. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

A computational study on the reactivity enhancement in the free radical polymerization of alkyl α‐hydroxymethacrylate and acrylate derivatives

The free radical polimerizability behavior of alkyl α‐hydroxymethacrylate (RHMA) derivatives ( M1–M3 ) has been modeled by considering the propagation of the dimeric units of the compounds of interest. All the transition structures in this class of monomers are stabilized by long‐range C?O…H? C interactions. The RHMA monomer bearing the ester functionality ( M2 ) polymerizes slightly faster than the one with the ether functionality ( M1 ) because of stronger electrostatic interactions between the C?O and H? C groups. 2‐(Methoxycarbonyl)allyl benzoate ( M3 ) shows higher reactivity as compared to M1 and M2 due to stronger electrostatic interactions. The same type of study has been carried out for hexyl ( M4 ), benzyl ( M5 ), and phenyl ( M6 ) acrylate derivatives whose increasing reactivity has been attributed to the presence of C?O…H? C, C?O…H‐? as well as π–π stabilizing interactions, respectively. While B3LYP/6‐31+G(d) has been used to locate the stationary points along the free radical polymerization of nonaromatic species, long‐range stabilizing interactions have only been detected with M06‐2X/6‐31+G(d). The kinetics that we obtain with this latter methodology for the free radical polymerization reactions of M1 – M6 agree well qualitatively with experiment. An implicit solvent model has reproduced the kinetics of M1–M3 in benzene the best. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Ru(Ⅱ)和Ru(Ⅲ)配合物[Ru(bpy)(PH3)(-C≡CC6H4NO2-p)Cl]m(m=0,+1)的光谱性质的密度泛函-含时密度泛函理论研究

我们利用DFT中的B3LYP方法优化了Ru(Ⅱ)配合物和氧化的Ru(Ⅲ)配合物[Ru(bpy)(PH3)(-C≡CC6H4NO2-p)Cl]m[bpy=2,2′-bipyridine;m=0(1), 1(1 )]的基态几何结构,得到的几何参数与实验结果吻合的很好。采用TDDFT方法,得到了配合物1和1 的激发态电子结构和电子吸收光谱。研究结果表明,配合物1和1 随着氧化过程的发生,光谱性质也发生变化,Ru(Ⅱ)配合物的低能吸收被指认为MLCT/LLCT混合跃迁,而氧化的Ru(Ⅲ)配合物1 的低能吸收具有LMCT跃迁性质。     

已烯自由基阳离子的密度泛函理论研究

使用密度泛函理论B3LYP方法和6-31G(d,p),6-31+G(d,p),6-311G(d,p)及6- 311+G(d,p)基组,分别对1-C_6H_(12)~+,2-C_6H_(12)~+和3-C_6H_(12)~+的各种构 象进行了几何构型优化,并在B3LYP/6-311G(d,p)水平上进行了频率分析计算,在 各优化构型上,使用B3LYP和MP2(full)方法进行了超精细结构的计算。计算的3- C_6H_(12)~+的超精细偶合常数比以往的计算结果更好;1-C_6H_(12)~+和2-C_6H_ (12)~+的超精细偶合常数目前尚无实验数据报道,本计算预言了它们的超精细偶合 常数和最稳定构型。     

Structures and properties of (H2GaN3)n (n = 1–4) clusters: A DFT study

Computations on the systems of (H₂GaN₃)_n (n = 1–4) are performed using the density functional theory (DFT)/B3LYP method with different basis sets. (H₂GaN₃)₂ possessing D_2h symmetry is found to exhibit the planar Ga₂N₂ ring structure. (H₂GaN₃)₃ involving a six‐membered Ga₃N₃ ring is found to exhibit two minima with very similar binding energies (ca. −235 ∼ −231 kJ · mol⁻¹). One minimum is the newly found boat‐like conformation possessing C_s symmetry. Another minimum possessing C_3v symmetry is the chair‐like conformation. (H₂GaN₃)₄ occurs in several structures with Ga₄N₄ eight‐membered ring structures that correspond to minima with slight energy differences among them. The structural changes of the clusters are large compared with the monomer. Frequency calculations are carried out on each optimized structure, and their infrared (IR) spectra are discussed. Thermodynamic properties demonstrate that the systems of H₂GaN₃ occur at dimer–trimer–tetramer equilibrium, and the trimer is the main component. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

戊烯自由基阳离子的密度泛函理论研究

使用密度泛函理论B3LYP方法和6-31G(d,p)、6-31＋G(d,p)、6-311G(d,p)及6-311＋G(d,p)基组，分别对2-C5H10＋和1-C5H10＋的各种构象进行了几何构型优化，并用B3LYP/6-311G(d,p)进行了频率分析计算.计算预言1-C5H10＋具有非平面构型，与以往报导的从头算计算结论相反.在两个自由基阳离子的各种构象的B3LYP几何构型上，进行了B3LYP和UMP2(full)方法的超精细偶合常数计算，得到了比以往更好的结果.     

Photo‐physical Properties of N‐methyl‐3,4‐fulleropyrrolidine and Its Derivatives: A DFT and TD‐DFT Investigation

A series of N‐methyl‐3,4‐fulleropyrrolidine (NMFP) derivatives were designed by selecting different π‐conjugated linkers and electron‐donating groups as D‐π‐A and D‐A systems. The optimised structures and photo‐physical properties of NMFP and its derivatives have been determined using density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) methods with the B3LYP functional and the 6‐31G basis set. According to the computation analysis, both the π‐conjugated linkers and the electron‐donating groups can influence the electronic and photo‐physical properties of the NMFP derivatives. Our calculated results demonstrated that the electron‐donating groups, with significant electron‐donating ability, had the tendency to increase the highest occupied molecular orbital (HOMO) energy. The π‐conjugated linkers with lower resonance energy decreased the lowest occupied molecular orbital (LUMO) energy and caused a significant decrease in the energy gap (E_g) between the E_HOMO and E_LUMO. A Natural Bond Orbital (NBO) analysis examines the effect of the electron‐donating group, π conjugated linker, and electron‐withdrawing group for these NMFP derivatives. For the NMFP derivatives, a projected density of state (PDOS) analysis demonstrated that the electron density of HOMO and LUMO are concentrated on the electron‐donating group and the π‐conjugated linker, respectively. A TD‐DFT/B3LYP calculation was performed to calculate the electronic absorption spectra of these NMFP derivatives. Both the electron‐donating group and the π‐conjugated linker contribute to the major absorption peaks, which are assigned as HOMO to LUMO transitions and are red‐shifted relative to those of non‐substituted NMFP.     

Substituent effect of large conjugate groups on the DNA base pair derivatives: Density functional study

The substituent effects caused by 2‐nitro‐naphthalen (aNO₂), 2‐hydroxyl‐naphthalen (aOH), 1‐nitro‐4‐vinyl‐benzene (bNO₂), and 1‐hydroxyl‐4‐vinyl‐benzene (bOH) have been investigated in this report. The geometries of various substituted base pairs have been optimized using the B3LYP method at the 6‐31G* level with no constraints. The vertical ionization potential energy has been calculated. Natural bond orbital (NBO) and CHelp analyses have also been carried out on both the neutral and cationic systems at the same level. The outcomes show that the hydrogen bond lengths of these substituted base pairs are similar to unsubstituted bases, while the geometries of the substituted bases have an interesting aspect; i.e., the substituent and the substituted base are nonplanar when the substituted base is pyrimide, while it is coplanar when the substituted base is purine. The stabilization energies changed slightly as compared with the corresponding A:T or G:C base pairs. NBO analysis shows that charge transfer is the largest in aOH‐T:A, while it is small in the other derivatives. Population analysis shows that the NPA and Mulliken charge of H has a relationship with the H‐bond lengths, while that of Chelp does not. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

A configurational and conformational study of aframodial and its diasteriomers via experimental and theoretical VA and VCD spectroscopies

In this work we present the experimental and theoretical vibrational absorption (VA) and the theoretical vibrational circular dichroism (VCD) spectra for aframodial. In addition, we present the theoretical VA and VCD spectra for the diasteriomers of aframodial. Aframodial has four chiral centers and hence has 2⁴ = 16 diasteriomers, which occur in eight pairs of enantiomers. In addition to the four chiral centers, there is an additional chirality due to the helicity of the entire molecule, which we show by presenting 12 configurations of the 5S,8S,9R,10S enantiomer of aframodial. The VCD spectra for the diasteriomers and the 12 configurations of one enantiomer are shown to be very sensitive not only to the local stereochemistry at each chiral center, but in addition, to the helicity of the entire molecule. Here one must be careful in analyzing the signs of the VCD bands due to the ‘non-chiral’ chromophores in the molecule, since one has two contributions; one due to the inherent chirality at the four chiral centers, and one due to the chirality of the side chain groups in specific conformers, that is, its helicity. Theoretical simulations for various levels of theory are compared to the experimental VA recorded to date. The VCD spectra simulations are presented, but no experimental VCD and Raman spectra have been reported to date, though some preliminary VCD measurements have been made in Stephens’ lab in Los Angeles. The flexible side chain is proposed to be responsible for the small size of the VCD spectra of this molecule, even though the chiral part of the molecule is very rigid and has four chiral centers. In addition to VCD and Raman measurements, Raman optical activity (ROA) measurements would be very enlightening, as in many cases bands which are weak in both the VA and VCD, may be large in the Raman and/or ROA spectra. The feasibility of using vibrational spectroscopy to monitor biological structure, function and activity is a worthy goal, but this work shows that a careful theoretical analysis is also required, if one is to fully utilize and understand the experimental results. The reliability, reproduceability and uniqueness of the vibrational spectroscopic experiments and the information which can be gained from them is discussed, as well as the details of the computation of VA, VCD and Raman (and ROA) spectroscopy for molecules of the complexity of aframodial, which have multiple chiral centers and flexible side chains. Festschrift in Honor of Philip J. Stephens’ 65th Birthday.     

A DFT study of the hydration of monophosphate complexes of iron (III),

A systematic theoretical DFT study of the bonding between the cation Fe³⁺ and the anion was carried out. The role of water ligands is presented. Several isomers with tetrahedral, bipyramidal and octahedral environments around the iron ion were investigated. 5-fold coordination of the Fe³⁺ cation is found when 5 and 6 water molecules are included. Calculated infrared spectra are also presented.     

Geometry and electronic structure of a heterometallic cluster Mo<Subscript>2</Subscript>Mg<Subscript>2</Subscript> in different oxidation states of Mo: a DFT study

Reduction of tetranuclear heterometallic complex Mo₂Mg₂ was simulated using the B3LYP and PBE density functional methods. The results of geometry calculations of the initial complex [Mo^VIO₂Mg(MeOH)₂(OMe)₄]₂ and a partially reduced Mo^V complex are in good agreement with experimental data. The reduced Mo^III complex is characterized by a decrease in the binding energy of aqua ligands. Structural rearrangement of the complex with release of a coordination position at the Mo atoms requires small energy expenditure. One can assume that the reduction of the polynuclear complex causes overcrowding of its coordination sphere, which favors formation of dinitrogen complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 441–457, March, 2008.     

DFT study on the effects of substituents on the structure and properties of dithiophosphate collectors

The structures and properties of seven substituted dithiophosphate (DTP) collectors containing three types of functional groups (O₂PS₂, C₂PS₂, and N₂PS₂) were studied using density functional theory. The collectors studied were dibutyl dithiophosphate (DNBDTP), diisobutyl dithiophosphate (DIBDTP), dibutoxyethyl dithiophosphate (DBOEDTP), xylenol dithiophosphate (DMPDTP), diisobutyl dithiohypophosphite (3418A), diphenylamine dithiophosphate (DTADTP), and dicyclohexylamine dithiophosphate (DCADTP). The structural analysis showed that the P S bond lengths in the C₂PS₂ and N₂PS₂ types are longer than those in the O₂PS₂ type, indicating that the strength of the P S bond is weaker in the former two. The frontier molecular orbital studies showed that the energy differences between the highest occupied molecular orbitals (HOMO) of 3418A (C₂PS₂ type) and DCADTP (N₂PS₂ type) and the lowest unoccupied molecular orbital (LUMO) of galena are significantly lower than those of the other collectors, suggesting that C₂PS₂ type and N₂PS₂ type with cyclohexane could enhance the interaction with galena. Using the Fukui function to calculate the nucleophilicity and electrophilicity of the sulfur atom indicated that the S atom exhibits nucleophilicity, especially in DMPDTP and DTADTP, which contain benzene rings, and the S atom exhibits strong nucleophilicity without electrophilicity. However, due to the lack of contribution from S atoms to the LUMO orbitals, the S atoms in these two compounds are not participate in any LUMO reactions. The adsorption results demonstrated that 3418A (C₂PS₂ type) and DCADTP (N₂PS₂ type) exhibit the strongest adsorption on Pb²⁺ ions, while DMPDTP (C₂PS₂ type) and DTADTP (O₂PS₂ type) which contain benzene rings, as well as DBOEDTP (C₂PS₂ type) which does not contain a benzene ring, exhibit weaker interaction compared to the other compounds. These are consistent with the results of the frontier molecular orbital and electrophilic nucleophilicity calculations.     

Protonation of 5‐methylhydantoin and its thio derivatives in the gas phase: A theoretical study

The gas phase proton affinities of 5‐methylhydantoin and its thio derivatives were theoretically studied through the use of high‐level density functional theory calculations. The structure of all possible tautomers and their conformers were optimized at the B3LYP/6‐311+(d,p) level of theory. Final energies were obtained at the B3LYP/6‐311+(2df,2p) level. The imidazolidone derivatives 5‐methyl‐2,4‐dioxo imidazolidine, 5‐methyl‐2‐oxo‐4‐thio imidazolidine, 5‐methyl‐2‐thio‐4‐oxo imidazolidine, and 5‐methyl‐2,4‐dithio imidazolidine possess moderately strong proton affinities. Protonation at sulfur would be larger than protonation at oxygen. The most stable protonated forms of 2O4O and 2S4O have the proton attached to the heteroatom in position 2, whereas protonation of 2O4S and 2S4S preferentially takes place at position 4. The barriers for proton migration between the different tautomers are rather large. The energy decomposition analysis analysis of the O? H⁺ and S? H⁺ interactions suggests that the bonding interactions come mainly from the covalent bond formation. The contribution of the Coulomb attraction is rather small. © 2012 Wiley Periodicals, Inc.     

DFT study on the role of methanol solvent in Morita–Baylis–Hillman reaction

B3LYP/6‐311++G** calculations have been carried out to study the role of methanol solvent in the trimethylamine‐catalyzed Morita‐Baylis‐Hillman reaction between acraldehyde and formaldehyde with CPCM solvent method and supramolecular model with one explicit CH₃OH solvent molecule, respectively. The optimized geometries and energies of the reactant complexes, intermediates, transition states, and products of the two reaction channels (corresponding to the scenarios of syn‐ and anti‐acraldehyde, respectively) were obtained, and the relative energy profiles were completed. The results reveal that CH₃OH solvent molecules can stabilize the zwitterionic intermediates and largely reduce the barrier of H transfer process by taking part in the formation of the transition state in this process. C? C bond formation step is the rate‐determining step of the whole reaction cycle. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

二阶非线性光学活性分子——咪唑类衍生物的设计与性质的理论研究

采用B3LYP方法在6-31G*水平上优化了6种F,Cl和Br取代的咪唑类衍生物分子几何构型,在此基础上采用TD-DFT的方法计算了它们的前线轨道能级和电子光谱,并用CPHF方法研究了此类衍生物二阶非线性光学系数性质.计算结果表明:此类化合物具有平面结构,共轭性较强;分子内设计的推拉电子基团增强分子内电荷转移,使前线分子轨道间的电子跃迁更容易;各体系具有较大的vβec和良好的透明性;咪唑环的引入增强了体系的热稳定性.这些结论对分子设计具有一定的指导意义.     

Synthesis and DFT study of the spectral behavior of new 4‐hydroxycoumarins

4‐Hydroxycoumarins are compounds with a lot of applications as drugs and herbicides. They have very interesting spectral and chemical properties, which are investigated theoretically and experimentally. Some new 4‐hydroxycoumarins with arylydene‐β‐ketoester or arylydene‐2,4‐pentanedione side chain were synthesized by two step synthetic scheme. Their structure was characterized by UV–vis, IR, and ¹H NMR methods. The spectral behavior of the optimized structures of these compounds was reproduced by the hybrid DFT methods B3LYP and B3P86 with 6‐31G** and aug‐cc‐pVDZ basis sets. Electronic excited states and vibrational frequencies were calculated. HF method was also used for comparison, because of the lack of electronic correlation. The theoretical spectra were compared with the experimental ones. A lot of compounds show good agreement between experimental and some of the theoretical data, especially obtained by aug‐cc‐pVDZ basis set. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Methyl and methane elimination in the gas phase reaction of zirconium atom with 2-butyne: A DFT study

<正>The mechanisms for CH_3- and CH_4-elimination in the gas phase reaction of ground-state Zr with 2-butyne has been investigated in detail using B3LYP method.For the elimination of CH_3,two mechanisms which are similar to those previously found for the reactions of Y and Zr with propyne are identified.The mechanism for the elimination of CH_4 was revealed as:Zr + CH_3C≡CCH_3→π-complex→TS(H-migration)→HZr-(H_2CCC)-CH_3→TS(C-C insertion)→(H_2CCC)-HZr-CH_3→TS(H-migration)→CH_4+ ZrC_3H_2.