DFT assessment of the spectroscopic constants and absorption spectra of neutral and charged diatomic species of group 11 and 14 elements

The spectroscopic constants and absorption spectra of neutral and charged diatomic molecules of group 11 and 14 elements formulated as [M₂]^+/0/? (M = Cu, Ag, Au), and [E₂]^+/0/? (E = C, Si, Ge, Sn, Pb) have been calculated at the PBE0/Def2‐QZVPP level of theory. The electronic and bonding properties of the diatomics have been analyzed by natural bond orbital analysis approach and topology analysis by the atoms in molecules method. Particular emphasis was given on the absorption spectra of the diatomic species, which were simulated by time‐dependent density functional theory calculations employing the hybrid Coulomb‐attenuating CAM‐B3LYP density functional. The simulated absorption spectra of the [M₂]^+/0/? (M = Cu, Ag, Au) and [E₂]^+/0/? (E = C, Si, Ge, Sn, Pb) species are in close resemblance with the experimentally observed spectra whenever available. The neutral M₂ and E₂ diatomics strongly absorb in the ultraviolet region, given rise to UVC, UVA and in a few cases UVB absorptions. In a few cases, weak absorbion bands also occur in the visible region. The absorption bands have thoroughly been analyzed and assignments of the contributing principal electronic transitions associated to individual excitations have been made. © 2014 Wiley Periodicals, Inc.     

Structural,electronic, and magnetoresponsive properties of triangular lanthanide clusters and their free‐standing nitrides

The molecular and electronic structures, stabilities, bonding features, and magnetoresponsive properties of three‐membered [c‐Ln₃]^+/0/? (Ln = La, Ce, Pr, Nd, Gd, Lu) and heterocyclic six‐membered [c‐Ln₃E₃]^q (Ln = La, Ce, Pr, Nd, Gd, Lu; E = C, N; q = 0 or 1) rings have been investigated by means of electronic structure calculation methods at the DFT level. The [c‐Ln₃]^+/0/? clusters are predicted to be bound with respect to dissociation to their constituent atoms, the estimated binding energies ranging from 45.8 to 2056.4 kJ/mol. The [c‐Ln₃] rings capture easily a planar three‐coordinated nitrogen atom at the center or above the center of the ring yielding the lanthanide nitride clusters [c‐Ln₃(μ₃‐N)] adopting a planar geometry, except [c‐La₃(μ₃‐N)] which exhibits pyramidal geometry. The [c‐Ln₃(μ₃‐N)] clusters are predicted to be bound, with respect to dissociation to N (⁴S) atom and [c‐Ln₃] clusters in their ground states, the binding energies ranging from 53.9 to 257.9 kcal/mol. The six‐membered [c‐Ln₃E₃]^q rings are predicted to be bound with respect to dissociation to LnE^q monomers in their ground states with dissociation energies in the range of 173.8 to 318.0 kcal/mol. Calculation of the NICS_zz‐scan curves of the clusters predicted a “hermaphrodic” magnetic response of the [c‐Ln₃]^+/0/? and heterocyclic six‐membered [c‐Ln₃E₃]^q rings, manifested by the coexistence of successive diatropic (aromatic) and paratropic (antiaromatic) zones. The [c‐La₃]^+/0/? and [c‐Lu₃]^? are predicted to be weakly antiaromatic, the [c‐Lu₃]^0/+, [c‐Lu₃C₃]⁺, and [c‐Lu₃N₃] double (σ+π) aromatic, and the [c‐Gd₃C₃] and [c‐Gd₃N₃]⁺ rings (σ+δ)‐aromatic systems. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011     

A Fully Phosphane‐Substituted Disilene

There is growing interest in compounds containing functionalized E=E multiple bonds (E=Si, Ge, Sn, Pb) because of their potential to exhibit novel physical and chemical properties. However, compounds containing multiple functionalizations are rare, with scarcity increasing with increasing degree of substitution. The first ditetrelene R₂E=ER₂ in which the E=E bond is substituted by four heteroatoms (other than Si) is described. The tetraphosphadisilene {(Mes)₂P}₂Si=Si{P(Mes)₂}₂ ( 7 ) is readily isolated from the reaction between SiBr₄ and [(Mes)₂P]Li, the latter of which acts as a sacrificial reducing agent. The structure of 7 is presented, while the bonding in, and stability of 7 were probed using DFT calculations.     

New Cu(I) Coordination Complexes Based on Tetrathiafulvalene Substituted Triazol‐pyridine Ligand: Synthesis,Properties and Theoretical Studies

Two Cu(I) complexes based on the thioethyl‐bridged triazol‐pyridine ligand with tetrathiafulvalene unit (TTF‐TzPy, L ), [Cu(I)(Binap)(L)]BF₄ ( 5 , Binap=2,2’‐bis(diphenylphosphino)‐1,1’‐binaphthyl) and [Cu(I)(Xantphos)(L)]BF₄ ( 6 , Xantphos=9,9‐dimethyl‐4,5‐bis(diphenylphosphino)‐xanthene), have been synthesized. All new compounds are characterized by elemental analyses, ¹H NMR and mass spectroscopies. The complex 5 has been determined by X‐ray structure analyses which shows that the central copper (I) ion assumes distorted tetrahedral geometry. The photophysical, computational and electrochemical properties of L and 5 ‐ 6 have been investigated. The most representative molecular orbital energy‐level diagrams and the spin‐allowed singlet? singlet electronic transitions of the three compounds have been calculated with density functional theory (DFT) and time‐dependent DFT (TD‐DFT). The luminescence bands of Cu(I) complexes 5 ‐ 6 have been assigned as mixed intraligand and metal‐to‐ligand charge transfer ³(MLCT+π→π^*) transitions through analysis of the photophysical properties and DFT calculations. The electrochemical studies reveal that 5 ‐ 6 undergo reversible TTF/TTF^+?/TTF²⁺ redox processes and one irreversible Cu⁺→Cu²⁺ oxidation process.     

Spontaneous Double Hydrometallation Induced by N→M Coordination in Organometallic Hydrides of Group 14 Elements

Our attempts to synthesise N→M intramolecularly coordinated diorganometallic hydrides L₂MH₂ [M=Si ( 4 ), Ge ( 5 ), Sn ( 6 )] containing the CH=N imine group (in which L is C,N‐chelating ligand {2‐[(2,6‐iPr₂C₆H₃)N=CH]C₆H₄}^?) yielded 1,1′‐bis(2,6‐diisopropylphenyl)‐2,2′‐spriobi[benzo[c][1,2]azasilole] ( 7 ), 1,1′‐bis(2,6‐diisopropylphenyl)‐2,2′‐spriobi[benzo[c][1,2]azagermole] ( 8 ) and C,N‐chelated homoleptic stannylene L₂Sn ( 10 ), respectively. Compounds 7 and 8 are an outcome of a spontaneous double hydrometallation of the two CH=N imine moieties induced by N→M intramolecular coordination (M=Si, Ge) in the absence of any catalyst. In contrast, the diorganotin hydride L₂SnH₂ ( 6 ) is redox‐unstable and the reduction of the tin centre with the elimination of H₂ provided the C,N‐chelated homoleptic stannylene L₂Sn ( 10 ). Compounds 7 and 8 were characterised by NMR spectroscopy and X‐ray diffraction analysis. Because the proposed N→M intramolecularly coordinated diorganometallic hydrides L₂MH₂ [M=Si ( 4 ), Ge ( 5 ), Sn ( 6 )] revealed two different types of reduction reactions, DFT calculations were performed to gain an insight into the structures and bonding of the non‐isolable diorganometallic hydrides as well as the products of their subsequent reactions. Furthermore, the thermodynamic profiles of the different reaction pathways with respect to the central metal atom were also investigated.     

Density functional study of structural, electronic, and optical properties of small bimetallic ruthenium-copper clusters

The structural, electronic, bonding, magnetic, and optical properties of bimetallic [Cu(n)Ru(m)](+/0/-) (n + m ≤ 3; n, m = 0-3) clusters were computed in the framework of the density functional theory (DFT) and time-dependent DFT (TD-DFT) using the full-range PBE0 nonlocal hybrid GGA functional combined with the Def2-QZVPP basis sets. Several low-lying states have been investigated and the stability of the ground state spinomers was estimated with respect to all possible fragmentation schemes. Molecular orbital and population analysis schemes along with computed electronic parameters illustrated the details of the bonding mechanisms in the [Cu(n Ru(m)](+/0/-) clusters. The TD-DFT computed UV-visible absorption spectra of the bimetallic clusters have been fully analyzed and assignments of all principal electronic transitions were made and interpreted in terms of contribution from specific molecular orbital excitations.     

Catalytic Asymmetric Iodocyclization of N‐Tosyl Alkenamides using Aminoiminophenoxy Copper Carboxylate: A Concise Synthesis of Chiral 8‐Oxa‐6‐Azabicyclo[3.2.1]octanes

A newly developed aminoiminophenoxy copper carboxylate ( L7 ‐Cu‐OAc)‐catalyzed asymmetric iodocyclization of N‐Tosyl alkenamides gave O‐cyclized products in good yields with high enantioselectivity. From the O‐cyclized products, a skeletal transformation was succeeded in the synthesis of biologically important chiral 8‐oxa‐6‐azabicyclo[3.2.1]octanes. DFT calculations suggested that the acetoxy anion of the [ L7 ‐Cu‐OAc] acts as a base to generate the anion of N‐Tosyl alkenamide substrates. The exchanged acetic acid reconstructs a new hydrogen‐bonding network between the catalyst and the substrates to accomplish the highly efficient asymmetric O‐iodocyclization of N‐Tosyl alkenamides.     

Electronic,bonding, and optical properties of 1d [CuCN]n (n = 1–10) chains, 2d [CuCN]n (n = 2–10) nanorings,and 3d [Cun(CN)n]m (n = 4, m = 2, 3; n = 10, m = 2) tubes studied by DFT/TD‐DFT methods

The electronic, bonding, and photophysical properties of one‐dimensional [CuCN]_n (n = 1–10) chains, 2‐D [CuCN]_n (n = 2–10) nanorings, and 3‐D [Cu_n(CN)_n]_m (n = 4, m = 2, 3; n = 10, m = 2) tubes are investigated by means of a multitude of computational methodologies using density functional theory (DFT) and time‐dependent‐density‐functional theory (TD‐DFT) methods. The calculations revealed that the 2‐D [CuCN]_n (n = 2–10) nanorings are more stable than the respective 1‐D [CuCN]_n (n = 2–10) linear chains. The 2‐D [CuCN]_n (n = 2–10) nanorings are predicted to form 3‐D [Cu_n(CN)_n]_m (n = 4, m = 2, 3; n = 10, m = 2) tubes supported by weak stacking interactions, which are clearly visualized as broad regions in real space by the 3D plots of the reduced density gradient. The bonding mechanism in the 1‐D [CuCN]_n (n = 1–10) chains, 2‐D [CuCN]_n (n = 2–10) nanorings, and 3‐D [Cu_n(CN)_n]_m (n = 4, m = 2, 3; n = 10, m = 2) tubes are easily recognized by a multitude of electronic structure calculation approaches. Particular emphasis was given on the photophysical properties (absorption and emission spectra) of the [CuCN]_n chains, nanorings, and tubes which were simulated by TD‐DFT calculations. The absorption and emission bands in the simulated TD‐DFT absorption and emission spectra have thoroughly been analyzed and assignments of the contributing principal electronic transitions associated to individual excitations have been made. © 2015 Wiley Periodicals, Inc.     

杂硼原子簇XB6+ (X=C,Si, Ge,Sn, Pb)的稳定性和芳香性

利用从头算MP2方法和密度泛函理论B3LYP和B3PW91方法, 研究了杂硼原子簇XB₆⁺ (X=C, Si, Ge, Sn, Pb)的结构、稳定性及化学键合情况. 对C, Si, Ge, B使用6-311+G(d)基组, 对Sn和Pb使用LANL2DZ赝势基组. 研究结果表明, 具有C_s对称性的假平面XB₆⁺ (X=C, Si, Ge, Sn, Pb)结构是势能面上的全域极小点, 其稳定性要高于C_6v对称性的锥形结构和C₂对称性的假锥形结构. 在B3LYP水平上, 对这些异构体的势能面的极小点进行了自然键轨道(NBO)的分析; 对最稳定构型的最高占据分子轨道(HOMO)和最低空轨道(LUMO)能级差、分子轨道(MO)和核独立化学位移(NICS)进行了计算和讨论. 分析了杂原子和硼原子间、相邻硼原子间的键合情况, 讨论了最稳定构型的芳香性质.     

Less Is More: Three‐Coordinate C,N‐Chelated Distannynes and Digermynes

We report here the synthesis of new C,N‐chelated chlorostannylenes and germylenes L³MCl (M=Sn( 1 ), Ge ( 2 )) and L⁴MCl (M=Sn( 3 ), Ge ( 4 )) containing sterically demanding C,N‐chelating ligands L^{3, 4} (L³=[2,4‐di‐tBu‐6‐(Et₂NCH₂)C₆H₂]^?_; L⁴=[2,4‐di‐tBu‐6‐{(C₆H₃‐2′,6′‐iPr₂)N=CH}C₆H₂]^?). Reductions of 1 – 4 yielded three‐coordinate C,N‐chelated distannynes and digermynes [L^{3, 4}M ]₂ for the first time ( 5 : L³, M=Sn, 6 : L³, M=Ge, 7 : L⁴, M=Sn, 8 : L⁴, M=Ge). For comparison, the four‐coordinate distannyne [L⁵Sn]₂ ( 10 ) stabilized by N,C,N‐chelate L⁵ (L⁵=[2,6‐{(C₆H₃‐2′,6′‐Me₂)N?CH}₂C₆H₃]^?) was prepared by the reduction of chlorostannylene L⁵SnCl ( 9 ). Hence, we highlight the role of donor‐driven stabilization of tetrynes. Compounds 1 – 10 were characterized by means of elemental analysis, NMR spectroscopy, and in the case of 1 , 2 , 5 – 7 , and 10 , also by single‐crystal X‐ray diffraction analysis. The bonding situation in either three‐ or four‐coordinate distannynes 5 , 7 , and 10 was evaluated by DFT calculations. DFT calculations were also used to compare the nature of the metal–metal bond in three‐coordinate C,N‐chelating distannyne [L³Sn]₂ ( 5 ) and related digermyme [L³Ge]₂ ( 6 ).     

(XNR)_4立方簇合物结构与稳定性的DFT研究

用密度泛函理论(DFT),在B3LYP/CEP-121G水平上,首次对(XNR)_4 [X = C, Si,Ge,Sn,Pb;R = H,CH_3,C(CH_3)_3,Si(CH_3)_3,C_6H_5]立方簇合物的 几何构型、电子结构、振动光谱和化学键性质进行了研究,并对其分子碎片(XNR) _2进行了相同方法的优化计算。结果表明,(CNR)_4对应原5种结构均不能稳定存在 。(XNH)_4对应原5种结构稳定性较低。对于同一取代基R,簇合物的稳定性大小顺 序为：(PbNR)_4>(SnNR)_4>(GeNR)_4>(SiNR)_4>(CNR)_4。     

A New Copper(I) Complex Based on Imidazole and Triphenylphosphine Ligands: Synthesis,Structure, Third‐Order NLO,and Fluorescence Properties

A new candidate [Cu(PPh₃)₂Him]Br ( 1 , PPh₃=triphenylphosphine, Him=1‐H‐imidazole) for nonlinear optical (NLO) materials has been synthesized and characterized crystallographically. The third‐order NLO optical properties were measured by the Z‐scan technique with an 8 ns pulsed laser at 532 nm. Compound 1 exhibits strong NLO absorptive abilities [α₂=(61±5)×10^?12] and effective self‐focusing performance [n₂=(15±3)×10^?18 m²·W^?1] in 1.01×10^?4 mol·dm^?3 DMF solution. The compound also exhibits luminescence in DMF solution at room temperature and shows narrow emission with maximum at 382 nm. The electronic structure and photoluminescent process were investigated by means of TD‐DFT calculations. The results suggest that the contribution to the frontier orbitals from the Cu? Br δ bond plays a crucial role in its linear optical properties, and the origin of luminescence is attributable to the π??→n transitions.     

Elucidating the Germanium Distribution in ITQ-13 Zeolites by Density Functional Theory**

ITQ-13 is a medium-pore zeolite that can be prepared in all-silica form and as silicogermanate with Si/Ge ratios as low as 3. Usually synthesised in the presence of fluoride, ITQ-13 is among the very few systems containing fluoride anions in two distinct cage types, cube-like d4r units and [4 ⋅ 5⁶] cages. Here, dispersion-corrected density functional theory (DFT) calculations are used to investigate the energetically most favourable Ge distributions for Si/Ge ratios between 55 and 6. The calculations show Ge atoms are incorporated at both the corners of d4r cages and at the basal plane of the [4 ⋅ 5⁶] cages, in accordance with ¹⁹F NMR spectroscopy. Two Ge atoms at adjacent corners of [4 ⋅ 5⁶] cages are stable at the highest Ge content considered (Si/Ge=6). Such a local environment has not yet been considered in the experimental literature. A calculation of the corresponding ¹⁹F NMR resonance points to overlap with other resonances, which might preclude its clear identification. Additional calculations investigate the variation of the dynamic behaviour of the fluoride anions as a function of the local environment as well as the selective defluorination of the [4 ⋅ 5⁶] cages.     

Synthesis,spectroscopic characterization,X-ray structure and DFT calculations of five-coordinated chlorocopper(II) complex with bis(3,5-dimethylpyrazol-1-yl)methane

The reaction of copper dichloride dihydrate and bis(3,5-dimethylpyrazol-1-yl)methane affords [Cu{H₂C(3,5-Me₂pz)₂}₂Cl]Cl · 3H₂O. The compound has been studied by IR, UV–Vis spectroscopy and X-ray crystallography. The electronic structure of the [Cu{H₂C(3,5-Me₂pz)₂}₂Cl]⁺ cation has been calculated with the density functional theory (DFT) method. The spin-allowed doublet–doublet electronic transitions of [Cu{H₂C(3,5-Me₂pz)₂}₂Cl]⁺ have been calculated with the time-dependent DFT method, and the UV–Vis spectrum of the title compound has been discussed on this basis.     

Time‐dependent density functional theory studies of the electronic absorption spectra of metallophthalocyanines of group IVA

Time‐dependent density functional theory (TD‐DFT) calculations were carried out in a comparative study of the electronic absorption spectra of lead(II) phthalocyaninate (PbPc), tin(II) phthalocyaninate (SnPc), tin(IV) dichlorophalocyaninate (PcSnCl₂), germanium(II) phthalocyaninate (GePc), and germanium (IV) dichlorophalocyaninate (PcGeCl₂) with the B3LYP method and LANL2DZ basis set. Our calculated bands correspond well with the experimental results. The electronic natures of all the bands in the absorption spectra are assigned and analyzed comparatively according to the calculated electronic transition contributions. With the increase of the dielectric constant from CHCl₃ to DMSO, all the electronic absorption bands are somewhat red shift, consistent with the shift rules measured experimentally. The radius of the central metals has great influence to the absorption spectra, especially for the B bands. The influence of the radius of the central metals to the absorption spectra of PcSnCl₂ and PcGeCl₂ is smaller than to the spectra of the nonplanar MPcs (M = Pb, Sn, and Ge). Axial ligands also greatly changed the electronic absorption spectra due to the change of the orbital energy level and the molecular symmetry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Structure and bonding energy analysis of cationic metal-ylyne complexes of molybdenum and tungsten, [(MeCN)(PMe3)4M≡EMes]+ (M = Mo, W; E = Si, Ge, Sn, Pb): a theoretical study

The molecular and electronic structures and bonding analysis of terminal cationic metal-ylyne complexes (MeCN)(PMe(3))(4)M≡EMes](+) (M = Mo, W; E = Si, Ge, Sn, Pb) were investigated using DFT/BP86/TZ2P/ZORA level of theory. The calculated geometrical parameters for the model complexes are in good agreement with the reported experimental values. The M-E σ-bonding orbitals are slightly polarized toward E except in the complex [(MeCN)(PMe(3))(4)W(SnMes)](+), where the M-E σ-bonding orbital is slightly polarized toward the W atom. The M-E π-bonding orbitals are highly polarized toward the metal atom. In all complexes, the π-bonding contribution to the total M≡EMes bond is greater than that of the σ-bonding contribution and increases upon going from M = Mo to W. The values of orbital interaction ΔE(orb) are significantly larger in all studied complexes I-VIII than the electrostatic interaction ΔE(elstat). The absolute values of the interaction energy, as well as the bond dissociation energy, decrease in the order Si > Ge > Sn > Pb, and the tungsten complexes have stronger bonding than the molybdenum complexes.     

Hypervalent silicon versus carbon: ball-in-a-box model

Why is silicon hypervalent and carbon not? Or why is [Cl? CH₃? Cl]^? labile with a tendency to localize one of its axial C? Cl bonds and to largely break the other one, while the isostructural and isoelectronic [Cl? SiH₃? Cl]^? forms a stable pentavalent species with a delocalized structure featuring two equivalent Si? Cl bonds? Various hypotheses have been developed over the years focusing on electronic and steric factors. Here, we present the so‐called ball‐in‐a‐box model, which tackles hypervalence from a new perspective. This model reveals the key role of steric factors and provides a simple way of understanding the above phenomena in terms of different atom sizes. Our bonding analyses are supported by computation experiments in which we probe, among other things, the shape of the S_N2 potential‐energy surface of Cl^? attacking a carbon atom in the series of substrates CH₃Cl, ^.CH₂Cl, ^..CHCl, and ^...CCl. Our findings for ClCH₃Cl^? and ClSiH₃Cl^? are generalized to other Group 14 central atoms (Ge, Sn, and Pb) and axial substituents (F).     

A Bis(silylenyl)pyridine Zero‐Valent Germanium Complex and Its Remarkable Reactivity

The synthesis, reactivity, and electronic structure of the unique germylone iron carbonyl complex [SiNSi]Ge⁰ →Fe(CO)₄ is reported. The compound was obtained in 49 % yield from the reaction of the bis(N‐heterocyclic silylenyl)pyridine pincer ligand SiNSi (1,6‐C₅NH₃‐[EtNSi(N^tBu)₂CPh]₂) with GeCl₂?(dioxane) to give the corresponding chlorogermyliumylidene chloride precursor [SiNSi]Ge^IICl⁺ Cl^? , which was further reduced with K₂Fe(CO)₄. Single‐crystal X‐ray diffraction analysis of [SiNSi]Ge →Fe(CO)₄ revealed that the Ge⁰ center adopts a trigonal‐pyramidal geometry with a Si‐Ge‐Si angle of 95.66(2)°. Remarkably, one of the Si^II donor atoms in the complex is five‐coordinated because of additional (pyridine)N→Si coordination. Unexpectedly, the reaction of [SiNSi]Ge →Fe(CO)₄ with GeCl₂?(dioxane) (one molar equivalent) yielded the first push–pull germylone–germylene donor–acceptor complex, [SiNSi]Ge →GeCl₂→Fe(CO)₄ through the insertion of GeCl₂ into the dative Ge⁰→Fe bond. The electronic features of the new compounds were investigated by DFT calculations.     

Systematic Access of Ternary Organotetrel-Copper Chalcogenide Clusters by [PhTE3]3− Anions (T=Si,Sn; E=S,Se)

Fragmentation reactions of organotetrel chalcogenide heteroadamantane-type clusters [(PhT)₄E₆] (T/E=Si/S ( 1 ); Si/Se; Sn/S, and Sn/Se) by addition of the corresponding sodium chalcogenide gave salts of the general formula Na₃[PhTE₃], with T/E=Si/S ( 2 ); Si/Se ( 3 ); Sn/S ( A ); Sn/Se ( 4 ). Reaction of these salts with [Cu(PPh₃)₃Cl] gave a series of organotetrel–copper chalcogenide clusters [(CuPPh₃)₆(PhTE₃)₂] with T/E=Si/S; ( 5 ), Si/Se ( 6 ), Sn/S ( 7 ) and Sn/Se ( 8 ). Compounds 5 – 8 share a common structural motif with two intact {PhTE₃} units coordinating a Cu₆ moiety, which was previously reported with other ligands, and for the Sn and Ge congeners only. If the Sn/Se reaction system was allowed to crystallize more slowly, single crystals of compound [(CuPPh₃)₆(PhSnSe₃)₃Cu₃SnSe] ( 9 ) were obtained, which are based on a larger cluster structure. Hence, 9 might form from 8 through incorporation of additional cluster fragments. The experimentally and quantum chemically determined optical properties were compared to related clusters.     

Theoretical studies on the electronic structures and spectroscopic properties of a series of novel N?C?N‐coordinating Pt(II) complexes

The electronic structures and spectroscopic properties of the three tridentate cyclometalated Platinum(II) complexes PtL¹Cl [L¹ = 1,3‐di(2‐pyridyl)‐5‐methyl‐benzene] ( 1 ), PtL²Cl [L² = 1‐(2‐pyridyl)‐3‐(1‐pyrazolyl)‐5‐methyl‐benzene] ( 2 ), and PtL³Cl [L³ = 1,3‐bis(1‐pyrazolyl)‐5‐methyl‐benzene] ( 3 ) were calculated to explore their spectroscopic nature. The geometry structures of 1 – 3 in the ground and excited states were optimized under the density functional theory (DFT) and the single‐excitation configuration interaction (CIS) level, respectively. The absorption and emission spectra in CH₂Cl₂ solution were calculated by the time‐dependent density‐functional theory (TD‐DFT) with the polarized continuum model solvent model. As revealed from the calculations, the LUMO of 1 and 2 are localized on phenyl and pyridyl, but that of 3 has 50.3% π*(pyrazolyl) and 47.8% π*(phenyl). The energy gap of the d‐d state was much greater than that of the CT transitions. With the replacement of pyridyl by pyrazolyl, the electron‐donating ability of N atom decreases, whereas the LUMO energy level increases. The lowest‐energy absorptions and emissions are blue‐shifted in the order 1 > 2 > 3 , which are assigned as the ILCT/MLCT/LLCT and ³ILCT/³MLCT/³LLCT characters, respectively. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010