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The N-(4-nitrophenyl)methacrylamide homopolymer (poly(4NPMA)) and copolymer of limonene with N-(4-nitrophenyl)methacrylamide (4NPMA-co-LIM) have been synthesized and characterized by FT-IR and NMR spectroscopic methods. The spectroscopic properties of poly(4NPMA) and 4NPMA-co-LIM were predicted using Density Functional Theory (DFT) calculations. The results have been compared with observed values, and they match with each other. Frontier orbital analysis (FMOs), global reactivity descriptors, MEP as well as Mulliken atomic charge were calculated with same method for poly(4NPMA) and 4NPMA-co-LIM. The physical properties of homopolymer of NPMA and its copolymer with D-Limonene were compared and evaluated. Thermal stabilities of homo and copolymer were investigated.

Magnetic response properties of 1,2,3,5-tetrazine derivatives including the newly synthesized 4,6-diphenyl-1,2,3,5-tetrazine have been studied computationally at the density functional theory (DFT) level. Calculations of magnetically induced current densities and induced magnetic fields show that the unsubstituted 1,2,3,5-tetrazine is almost as aromatic as benzene. Separating the magnetic shielding functions into molecular orbital components provided additional insights into the magnetic response. The aromatic character estimated from magnetically induced current densities and induced magnetic fields shows that NICS pi zz(0) values and ring-current strengths yield about the same degree of aromaticity, whereas NICSzz(0) and NICSzz(1) values are contaminated by sigma electron contributions. The studied 1,2,3,5-tetrazine derivatives are less aromatic than the unsubstituted one. Calculations of magnetic response properties of 4,6-diphenyl-1,2,3,5-tetrazine showed that it is the least aromatic among the studied molecules according to the ring-current criterion, while 4,6-[1,2,3,5]-ditetrazinyl-1,2,3,5-tetrazine is as aromatic as 4,6-dimethyl-1,2,3,5-tetrazine and slightly less aromatic than the unsubstituted 1,2,3,5-tetrazine.

The effect of methanol group on absorption of SO2 by diamine compound was investigated via density functional theory. It was observed that the presence of methanol group increases the binding energy of absorption. According to the result of binding energy, the di-methanol-diamine (D-b) structure can be the best diamine for SO2 absorption and the results of Gibbs energy verified the most thermodynamically favorable structure. According to the weak energy analysis, the absorption interactions in D-b are both vdW and HB interactions. The result of second-order perturbation energy showed that the interaction of the donor atom of diamine with antibonding orbital of S-O (BD*S) in D-b is the highest which points to the most stable structure. According to molecular frontier orbital analysis, it can be concluded that the absorption of SO2 on the diamines is not very strong and desorption of SO2 would be easier than that the strong chemical absorption.

TcO3 + and TcO3(OH) along with their S and Se analogs, TcS3 +, TcSe 3 + ,TcS3(OH) and TcSe3(OH), have been analyzed employing the hybrid meta-GGA functional TPSS. Charge, geometry, frontier orbital analysis based on the optimized structure have been done as a function of type of an atom bonded to Tc. The effect of addition of OH− group to TcS3 +, TcSe 3 + and TcO3 + on geometrical and electronic properties is discussed. Rotational barrier of the O–H bond for title molecules are calculated and discussed.

A combination of computational techniques was used to study the phosphorescent emission of complexes with general formula [Cu 3 ( μ -dppm) 3 ( μ 3 - η 1 -C≡CAr) 2 ]BF 4 , with Ar = aryl. The calculated S 0 –T 1 transition energies are in good agreement with the experimental emission maxima. Natural Transition Orbital analysis of the lowest triplet states indicates that the emission largely originates from a π → π* excitation on one of the two acetylide ligands with only a marginal participation of the trinuclear copper(I) cluster, unlike previously proposed.

The binding behaviors of eight bivalent metalloporphyrins (MPs) (MZn, Mg, Cu, Mn, Fe, Co, Ni, and Cd) with NH3 were investigated by density functional theory. For both MPs and corresponding complexes MPs-NH3, good linear correlations are found between the partial charge on metal M and that on atom N (nitrogen of porphyrin) as well as the MN bond length. Natural population and frontier orbital analysis demonstrate that charge transfer in CoP-NH3 is much easier and greater. As a consequence of the charge transfer and the hybridization of molecular energy levels, striking disparities of electronic properties of MPs-NH3 are observed. Particularly, a modest linear relationship is obtained between the magnitude of charge transfer and the binding energy. The much greater Fukui functions of CoP, together with its larger binding strength, suggest that CoP is more favorable to the interaction with NH3, which might be a promising sensing material to response NH3. © 2013 Wiley Periodicals, Inc.

We report results of hyperpolarizability calculations on CdnXn (X: S, Se and Te; n = 1–10) clusters. Our results show that the geometric configurations of different types of clusters under investigation are quite similar at specific values of n. Both static and frequency dependent components of first and second order hyperpolarizability tensors of CdnSn, CdnSen and CdnTen are compared. It is observed that in general nonlinear optical coefficients show identical variation in all the cluster materials. The present investigation also manifests the improvement of these coefficients due to the introduction of asymptotically correct generalized gradient approximation functional over the local density functional and normal gradient corrected functional. Symmetrized fragment orbital analysis has been performed to provide explanation of the observed hyperpolarizability variation. We also analyse how geometries with closely lying energy values influence the hyperpolarizabilities of these cluster materials.

Using hybrid density functional theory and a relatively large basis set, the lowest energy equilibrium structure, vibrational spectrum, and natural orbital analysis were obtained for magnesium diboride clusters [(MgB2)x for x=1,2, and 3]. For comparison, boron clusters [Bx for x=2,4, and 6] were also considered. The MgB2 and (MgB2)2 showed equilibrium structures with the boron atoms in arrangements similar to what was obtained for pure boron atoms, whereas, for (MgB2)3 a different arrangement of boron was obtained. From the population analysis, large electron density in the boron atoms forming the clusters was observed.

The equilibrium geometries, energies, harmonic vibrational frequencies, stability, and aromaticities for the [Formula: see text], E 4 Fe , and [ Fe (η4 - E 4)2]2- ( E = N, P, As, Sb, and Bi ) species are studied using density functional theory (DFT). The ground states of the E 4 Fe and [ Fe (η4 - E 4)2]2- systems are predicted to be Cs and D4d structures, respectively. Orbital analysis indicates that the orbital interactions between the π orbitals of the ligands and the atomic orbitals of the d 6 iron center are the main bonding scheme for these [ Fe (η4 - E 4)2]2- (D4d) complexes. The stability of the [ Fe (η4 - E 4)2]2- complexes exhibits the order P > As > Sb > Bi > N for E. On the basis of comparison with the known ferrocene, the NICS analysis confirms that the [ Fe (η4 - E 4)2]2- (D4d) as well as ferrocene are aromatic. The dissected NICS reveals that the aromaticities of the [ Fe (η4 - E 4)2]2- (D4d) are primarily attributed to the effects of their E–E π bonds and Fe lone pairs.

Density functional theory as well as Møller-Plesset investigations has been carried out on tetrafluoro cyclobutadiene, C4F4, to explore the origin of its nonplanarity. Although Petersson et al. (Petersson, E. J.; Fanuele, J. C.; Nimlos, M. R.; Lemal, D. M.; Ellison, G. B.; Radziszewski, J. G. J. Am. Chem. Soc. 1997, 119, 11122-11123) had earlier predicted a nonplanar geometry of this compound on the basis of spectral and bond orbital analysis, the explanation of the same from a more fundamental point of view is still missing. In the present study, we provide a heuristic explanation for the origin of nonplanarity of C4F4. The two major driving forces behind this nonplanar geometry are the unusual aromaticity of this cyclic homoatomic 4pi electron system and the second-order Jahn-Teller effect (SOJTE). These driving forces can well be explained by various energy and density parameters and also by nucleus-independent chemical shift (NICS) values. Aromaticity of a cyclic homoatomic 4pi electron system is quite remarkable. The enhancement of pi- delocalization as evidenced from molecular orbital analysis may be attributed to s-ppi mixing in nonplanar C4F4.

Studying the interaction of some atmospheric gases (H2O, HCN, NH3, SO3 and H2S) with 3PT oligomers is important in the development of polymeric sensors for gas detection. In the present study, we studied the relaxed geometries, interaction energies, charge analysis, HOMO-LUMO orbital analysis, and UV-vis spectra of all interacted systems using first-principles density functional theory (DFT). All these analyses indicated the potential of polythiophene as an inexpensive polymeric sensor for the analytes mentioned. Interaction energy values of -19.90, -19.66, -14.01, -8.70, and -4.76 kJ mol(-1) were achieved for adsorption of SO3, H2O, NH3, HCN, and H2S on 3PT, respectively. Consequently, clarification of their physical parameters became the major focus of this study.

Density functional theory has been used to explore the energetics and bonding of the symmetric and unsymmetric isomeric sandwich complexes (η 5 -C 5 H 5 ) 2 M, (η 4 -C 4 H 4 )M(η 6 -C 6 H 6 ), and (η 3 -C 3 H 3 )M(η 7 -C 7 H 7 ) (M = Fe, Ru, Os). For each metal atom, the symmetric “5–5” metallocene was found to be the most stable isomer, with the “4–6” and “3–7” isomers ca. 40 and 80 kcal/mol higher in energy, respectively. Bonding analysis shows that (η 4 -C 4 H 4 )Fe(η 6 -C 6 H 6 ) is best considered as a (η 4 -C 4 H 4 )Fe fragment interacting with a C 6 H 6 ligand, although the interactions become less separable as the metal is changed to Ru and Os. Similarly, the dominant bonding in (η 3 -C 3 H 3 )M(η 7 -C 7 H 7 ) is that of a M(η 7 -C 7 H 7 ) perturbed by the interaction with a C 3 H 3 ligand.

A first-principles study of the dissociative adsorption of water on Ge(100)-(2 x 1) is described, on the basis of density functional theory with a cluster model of the surface. Experiments have shown that water incident on the Ge(100)-(2 x 1) surface has a very small probability of dissociative adsorption, indicating the presence of an activation barrier. This is in contrast to the analogous reaction on Si(100)-(2 x 1), which is unactivated. This difference is reproduced in the calculations, demonstrating the predictive capability of the methods used, though some caveats about basis sets are necessary. A frontier orbital analysis is used to identify the interactions that determine the transition state energy and underlie the difference between reactivity on Si and Ge.

The unrestricted Hartree-Fock (UHF) and hybrid density functional theory (HDFT) calculations have been carried out for manganese oxides. In order to elucidate magnetic properties of the species, the effective exchange integrals ( J ab ) have been obtained by the total energy difference between the highest and lowest spin states. The natural orbital analysis has also been performed for elucidation of symmetry and occupation numbers of the magnetic orbitals.

A novel Au19 nanocluster with a composition of [Au19(PhC≡C)9(Hdppa)3](SbF6)2 was synthesized (Hdppa = N,N-bis(diphenylphosphino)amine). Single crystal X-ray structural analysis reveals that the cluster comprises a centered icosahedral Au13 core hugged by three V-shaped PhC≡C–Au–C≡C(Ph)–Au–C≡CPh motifs. Such motif is observed for the first time in an alkynyl-protected gold nanocluster. The Au19 cluster shows two main optical-absorption bands at 1.25 and 2.25 eV, confirmed by time-dependent density functional theory. Orbital analysis indicates that PhC≡C– groups can actively participate in the frontier orbitals of the whole cluster. The new Au19 cluster and the novel alkynyl–gold motif open the door to understanding the alkynyl–gold interface and discovering many potential members of this new class of gold clusters.

Density functional theory based calculations are performed to study structures and properties of coupled tetragonal pyramid (CTP) Pt7 based Pt7−x Ru x (x = 1, 2, 3) clusters as well as their interactions with a CO molecule. Among the PtRu isomers studied, the clusters with the Ru atoms occupy the bottom sites of CTP Pt7 are more stable than other homotops. Furthermore, the bimetallic clusters are more stable than Pt7 and the most stable one is aPt5Ru2. The natural orbital analysis shows that the charge transfer from Ru to Pt atoms enhancing the stability of PtRu clusters. Frontier molecular orbital theory is used to predict the selectivity of CO adsorption on these metal clusters. The adsorption energy, CO bond stretching frequency, geometries of the PtRu-CO system and electronic-structure details have been investigated about the interaction between CO and metal clusters. The CO prefers to adsorb on Pt than on Ru and the adsorption energy on Pt will decrease with increasing of Ru content. Electronic-structure details are discussed to explain the observed results and analyze the interaction between CO and metal clusters.

Armchair graphene nanoribbons and their derived structures containing Stone–Wales defects are investigated using a self-consistent field crystal orbital method based on density functional theory. The investigation indicates that both the nanoribbons and the defective structures are semiconductors. A low concentration of middle Stone–Wales defects generally increases the carrier mobility, calculated using deformation potential theory, while edge Stone–Wales defects decrease it. The largest increment of the carrier mobility is as high as 170%, which is explained by the lighter carrier effective mass with crystal orbital analysis.

The homodinuclear [ClM(mu-dppm)(2)MCl] complexes 1 (M = Pd) and 2 (M = Pt) react with RNC ligands (R = Ph, xylyl, p-tolyl, p-C(6)H(4)iPr) to provide the A-frame [ClPd(mu-dppm)(2)(mu-C=N-R)PdCl] (R = Ph (5a), xylyl (5b)), [ClPt(mu-dppm)(2)(mu-C=N-R)PtCl] (R = p-tolyl (4a); p-C(6)H(4)iPr (4b)), and the d(9)-d(9) M(2)-bonded [ClPt(mu-dppm)(2)Pt(CN-R)]Cl (R = xylyl (3a); p-C(6)H(4)iPr (3b)) complexes. The heterodinuclear [XPd(mu-dppm)(2)PtX] complexes 6a (X = Cl) and 6b (X = I) react with RNC (R = o-anisyl) to form the A-frame [XPd(mu-dppm)(2)(mu-C=N-R)PtX] (X = Cl (9); I (10a)) and M(2)-bonded [ClPt(mu-dppm)(2)Pt(CN-R)]Cl (10b) complexes. The dangling ligand-containing complex [ClPd(mu-dppm)(2)Pt(eta(1)-dppm=O)](BF(4)) (7) reacts with xylyl-NC stoichiometrically to produce the dicationic salt [(xylyl-NC)Pd(mu-dppm)(2)Pt(eta(1)-dppm=O)](BF(4))(2) (8). Parameters ruling the coordination site terminal versus bridging are discussed. The precursor 10a reacts with RNC (R = o-anisyl, tBu) to form the heterobimetallic bis(isonitrile) [IPd(mu-dppm)(2)(mu-C=N-o-anisyl)Pt(CN-R)]I complexes 11b and 12, respectively, demonstrating the site selectivity of the second CNR ligand coordination, Pd versus Pt. The X-ray structures of 11b and 12 were obtained. Complex 12 is the first example of an A-frame system of the Ni-triad bearing two different isocyanide ligands. Several d(9)-d(9) terminal and d(8)-d(8) A-frame homo- and heterodinuclear complexes in 2-MeTHF at 77 K were studied by UV-vis and luminescence spectroscopy. Assignments for the lowest energy absorption and emission bands are made on the basis of density functional theory and time-dependent density functional theory computations.

Frozen-orbital analysis (FZOA), which has been proposed in order to analyze excitations between degenerate orbitals, is extended to the Tamm―Dancoff approximation to time-dependent density functional theory (TDDFT/TDA). FZOA for TDDFT/ TDA with BLYP and B3LYP is applied to a CO molecule, and the difference between TDDFT/TDA and configuration interaction singles (CIS) is discussed.