Approximate MCSCF optimization for multiconfigurational spin‐tensor electron propagator method (MCSTEP): The vertical ionization potentials of CO,HCN, HNC,H2CO,and O3

The multiconfigurational spin tensor electron propagator method (MCSTEP) was developed as an implementation of electron propagator/single particle Green's function methods. MCSTEP was specifically designed for open shell and highly correlated (nondynamically correlated) initial states. The initial state used in MCSTEP is typically a small complete active space (CAS) with multiconfigurational self‐consistent field (MCSCF) state. In some cases, because of our use of a small CAS in MCSTEP, the Lagrangian eigenvalues of the MCSCF reference state are in an undesired order (u). The desired order (d) can usually be obtained by excluding one or more orbital rotations in MCSCF optimization between the doubly occupied and partially occupied orbitals. We systematically examine several cases where the undesired order occurs for the low‐lying vertical MCSTEP ionization potentials (IPs) of the molecules CO, HCN, HNC, H₂CO, and O₃ with our recently established CAS choices for MCSCF/MCSTEP. By excluding one or more orbital rotations between the partially and doubly occupied orbitals, an approximate MCSCF reference state with the same CAS choice is obtained for use in standard MCSTEP calculations that, in general, gives more reliable vertical MCSTEP IPs. © 2007 Wiley Periodicals, Inc. J Quantum Chem, 2008     

Modification of optimal complete active space choices for the multiconfigurational spin‐tensor electron propagator method for ionization potentials

The multiconfigurational spin tensor electron propagator (MCSTEP) method was developed as an implementation of electron propagator/single particle Green's function methods. MCSTEP was specifically designed for open‐shell and highly correlated (nondynamically correlated) initial states. Ionization or electron attachment is always from a state of pure spin symmetry to a state of pure spin symmetry even if the initial state is open shell. MCSTEP can be used as well for molecules with initial states that can be accurately described by a single determinant‐based theory. The initial state that is used in MCSTEP is typically a small complete active space (CAS) multiconfigurational self‐consistent field (MCSCF) state. We previously examined different small CAS choices for MCSTEP initial states and have developed a generally workable scheme. This article further examines some different ways to choose the CAS for MCSTEP. With several logical CAS choices, we have calculated the low‐lying vertical MCSTEP ionization potentials (IPs) of C₂, N₂, linear H₂O, O₂, CH₂, and NH₂, comparing them with large multireference configuration interaction (MRCI) calculations. We conclude that generally a small modification and extension of our previous schemes for choosing the MCSTEP CAS gives IPs that most effectively mimics the results of large scale MRCI IPs in general. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

The multiconfigurational spin tensor electron propagator method (MCSTEP): Comparison with extended Koopmans' theorem results

Summary We applied the multiconfigurational spin tensor electron propagator method (MCSTEP) for determining the lowest few (in energy) vertical ionization potentials (IPs) of HF, H₂O, NH₃, CH₄, N₂, CO, HNC, HCN, C₂H₂, H₂CO, and B₂H₆. We chose these molecules so that we could compare MCSTEP IPs with recently reported extended Koopmans' theorem (EKT) IPs on the same molecules. Using standard Dunning core-valence basis sets with relatively small complete active spaces, MCSTEP results are in very good to excellent agreement with experiment. These MCSTEP IPs are obtained using matrices no larger than 400 × 400. EKT matrices are even smaller; however, to obtain similar but generally slightly worse agreement with experiment, fairly large active spaces are required with EKT.     

Implementation and use of a direct, partially integral-driven non-Dyson propagator method for molecular ionization

The Green's function ADC(3) scheme has been for many years a successful method to predict theoretically the ionization (and electron affinity) spectrum of molecules. However, a dramatic enhancement of the method's power has come only recently, with the development of an approximation method to the one-particle Green's function which does not make direct use of the Dyson equation. In the present work, we present an efficient computer implementation of this novel approach, with first comparative tests demonstrating its enormous computational advantage over the conventional approach.     

Calculation of molecular response properties with the second‐order coupled perturbed electron propagator

We present the theory of the electron propagator perturbed by an external electric field and show how it can be used to calculate a variety of one‐electron linear response properties that are accurate through second order in electron correlation. Some illustrative calculations are discussed. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 625–640, 2000     

Reductive Hydrogenation of Cs‐C70(CF3)8 and C1‐C70(CF3)10

CF₃‐derivatized fullerenes prove once again to be promising scaffolds for regioselective fullerene functionalization: now with the smallest possible addends—hydrogen atoms. Hydrogenation of C_s‐C₇₀(CF₃)₈ and C₁‐C₇₀(CF₃)₁₀ by means of reduction with Zn/Cu couple in the presence of water proceeds regioselectively, yielding only one major isomer of C₇₀(CF₃)₈H₂ and only two for C₇₀(CF₃)₁₀H₂, whose addition patterns are combined in the only abundant isomer of C₇₀(CF₃)₁₀H₄. The observed selectivity is governed by the electronic structure of trifluoromethylated substrates. Interestingly, we discovered that Clar's theory can be utilized to predict the regiochemistry of functionalization, and we look forward to testing it on forthcoming cases of derivatization of pre‐functionalized fullerene building blocks.     

Fourier grid Hamiltonian‐based multidimensional Floquet propagator method for continuous,pulsed, and bichromatic laser field: Application to the multiphoton dissociation dynamics of HCN molecule

We present a Fourier grid Hamiltonian‐based multidimensional propagator method for multiphoton dissociation dynamics of triatomic molecule in continuous, pulsed, and bichromatic laser field. The method has been successfully applied to the photodissociation dynamics of HCN molecule, i.e., collinear geometry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Quantification and remote detection of nitro explosives by helium plasma ionization mass spectrometry (HePI‐MS) on a modified atmospheric pressure source designed for electrospray ionization

Helium Plasma Ionization (HePI) generates gaseous negative ions upon exposure of vapors emanating from organic nitro compounds. A simple adaptation converts any electrospray ionization source to a HePI source by passing helium through the sample delivery metal capillary held at a negative potential. Compared with the demands of other He‐requiring ambient pressure ionization sources, the consumption of helium by the HePI source is minimal (20–30 ml/min). Quantification experiments conducted by exposing solid deposits to a HePI source revealed that 1 ng of 2,4,6‐trinitrotoluene (TNT) on a filter paper (about 0.01 ng/mm²) could be detected by this method. When vapor emanating from a 1,3,5‐trinitroperhydro‐1,3,5‐triazine (RDX) sample was subjected to helium plasma ionization mass spectrometry (HePI‐MS), a peak was observed at m/z 268 for (RDX●NO₂)^?. This facile formation of NO₂^? adducts was noted without the need of any extra additives as dopants. Quantitative evaluations showed RDX detection by HePI‐MS to be linear over at least three orders of magnitude. TNT samples placed even 5 m away from the source were detected when the sample headspace vapor was swept by a stream of argon or nitrogen and delivered to the helium plasma ion source via a metal tube. Among the tubing materials investigated, stainless steel showed the best performance for sample delivery. A system with a copper tube, and air as the carrier gas, for example, failed to deliver any detectable amount of TNT to the source. In fact, passing over hot copper appears to be a practical way of removing TNT or other nitroaromatics from ambient air. Copyright © 2012 John Wiley & Sons, Ltd.     

DFT,CBS‐Q,W1BD and G4MP2 calculation of the proton and electron affinities,gas phase basicities and ionization energies of saturated and unsaturated carboxylic acids (C1–C4)

The proton affinities, gas phase basicities and ionization energies of formic acid, acetic acid, propanoic acid, 2‐propenoic acid, propiolic acid, butanoic acid, 2‐butenoic acid, 3‐botenoic acid, 2‐methyl‐propanoic acid and 2‐methyl‐2‐propenoic acid were calculated using the computational methods including B3LYP/6‐311++G(2df,p), CBS‐Q and G4MP2. Also, the considered properties were calculated using W1BD method only for formic and acetic acids. In addition, the electron affinities of the acids were calculated using B3LYP, CBS‐Q, G4MP2 and G2MP2 methods, separately. The calculations showed that the PA and gas phase basicity increase with the increase in the number of carbon atoms. The calculated Ionization energies of the unsaturated carboxylic acids are less than the corresponding saturated acids, which are in good agreement with the experimental results. © 2013 Wiley Periodicals, Inc.     

The grafting of acrylamide onto poly(ε‐caprolactone) and poly(1,5‐dioxepan‐2‐one) using electron beam preirradiation. III. The grafting and in vitro degradation of chemically crosslinked poly(1,5‐dioxepan‐2‐one)

Acrylamide was graft polymerized onto the surface of a chemically crosslinked and amorphous biodegradable polyester, poly(1,5‐dioxepan‐2‐one). Electron beam irradiation at a dose of 5 Mrad was used to generate the initiating species in the polyester. The degradation behavior in vitro at pH 7.4 and 37°C in a phosphate buffer solution was studied for untreated, irradiated, and acrylamide‐grafted polymer. Differences in weight loss performance were observed between virgin and treated polymers. The acrylamide‐grafted poly(1,5‐dioxepan‐2‐one) was totally degraded after 43 weeks as compared to 48 weeks for the irradiated and 55 weeks for the virgin polymer. On the other hand, the treated polymers showed a higher resistance to degradation in terms of weight loss during the intermediate part of the degradation, i.e., between about 5 and 35 weeks. After this period, the irradiated and particularly the acrylamide grafted poly(1,5‐dioxepan‐2‐one) degraded much more rapidly than the virgin polymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1659–1663, 1999     

The grafting of acrylamide onto poly(ε‐caprolactone) and poly(1,5‐dioxepan‐2‐one) using electron beam preirradiation. I. Influence of dose and Mohr's salt for the grafting onto poly(ε‐caprolactone)

Poly(ε‐caprolactone) films (TONE® 787) were irradiated by electron beam in air prior to grafting in aqueous solutions of acrylamide. The grafting kinetics and molecular weight of the grafted poly(acrylamide) chains were studied with irradiation doses between 2.5 and 20 Mrad and in the Mohr's salt concentration range of 0.0025–1 wt %. The grafting rate and yield were strongly dependent on the Mohr's salt concentration. By molecular weight analysis of grafted poly(acrylamide) chains, it was shown that the molecular weight is approximately proportional to the mass of the grafted PAAm. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1643–1649, 1999     

The grafting of acrylamide onto poly(ε‐caprolactone) and poly(1,5‐dioxepan‐2‐one) using electron beam preirradiation. II. An in vitro degradation study on grafted poly(ε‐caprolactone)

Acrylamide was graft polymerized onto the surface of a biodegradable semicrystalline polyester, poly(ε‐caprolactone). Electron beam irradiation at a dose of 5 Mrad was used to generate initiating species in the polyester. The degradation in vitro at pH 7.4 and 37°C in a phosphate buffer solution was studied for untreated, irradiated and acrylamide‐grafted polymers. In the case of poly(ε‐caprolactone), all materials showed similar behavior in terms of weight loss. No significant decrease in weight was observed up to 40 weeks, after which the loss of weight accelerated. The main differences in degradation behavior were found for the average molecular weights, M̄_n and M̄_w. Virgin poly(ε‐caprolactone) maintained M̄_n and M̄_w up to about 40 weeks, whereas the irradiated and grafted poly(ε‐caprolactone) showed similar continuous declines in M̄_n and M̄_w throughout the degradation period. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1651–1657, 1999     

Search of truncation of (N−1) electron basis containing full connected triple excitations in computing main and satellite ionization potentials via Fock‐space coupled cluster approach

A valence‐universal multireference coupled cluster (VUMRCC) theory, realized via the eigenvalue independent partitioning (EIP) route, has been implemented with full inclusion of triples excitations for computing and analyzing the entire main and several satellite peaks in the ionization potential spectra of several molecules. The EIP‐VUMRCC method, unlike the traditional VUMRCC theory, allows divergence‐free homing‐in to satellite roots which would otherwise have been plagued by intruders, and is thus numerically more robust to obtain more efficient and dependable computational schemes allowing more extensive use of the approach. The computed ionization potentials (IPs) as a result of truncation of the (N−1) electron basis manifold involving virtual functions such as 2h‐p and 3h‐2p by different energy thresholds varying from 5 to 15 a.u. with 1 a.u. intervals as well as thresholds such as 20, 25, and 30 a.u. have been carefully looked into. Cutoff at around 25 a.u. turns out to be an optimal threshold. Molecules such as C₂H₄ and C₂H₂ (X = D,T), and N₂ and CO (X = D,T,Q) with Dunning's cc‐pVXZ bases have been investigated to determine all main and 2h‐p shake‐up and 3h‐2p double shake‐up satellite IPs. We believe that the present work will pave the way to a wider application of the method by providing main and satellite IPs for some problematic N‐electron closed shell systems. © 2013 Wiley Periodicals, Inc.     

Peripheral or nonperipheral tetra‐[4‐(9H‐carbazol‐9‐yl)phenoxy] substituted cobalt(II), manganese(III) phthalocyanines: Synthesis,acetylcholinesterase, butyrylcholinesterase,and α‐glucosidase inhibitory effects and anticancer activities

In this work, peripheral or nonperipheral tetra‐[4‐(9H‐carbazol‐9‐yl)phenoxy] substituted cobalt(II), manganese (III) phthalocyanines were synthesized for the first time. Their acetylcholinesterase from Electrophorus electricus (AChE), butyrylcholinesterase equine serum (BuChE), and α‐glucosidase Saccharomyces cerevisiae inhibition were investigated spectrophotometrically. Finally, in vitro cytotoxicities of the compounds were investigated on human neuroblastoma (SH‐SY5Y) cell line using MTT cell viability assay. The compounds inhibited to enzymes in the range of 7.39 ± 0.25–35.29 ± 2.49 μM with IC₅₀ values for AChE and 14.38 ± 0.66–58.02 ± 4.94 μM for BuChE as compared with galantamine, which used as a positive control. For α‐glucosidase, all compounds had stronger inhibition action than acarbose according to the IC₅₀ values. The IC₅₀ values of N? Co and N? Mn were found to be 3.05 ± 0.10 and 15.82 ± 1.85 μM, respectively. The results of cytotoxicity showed that the IC₅₀ values were above 100 μM showing the compounds had low cytotoxic action against SH‐SY5Y cell line for 24 h. Overall, carbazole substituted nonperipheral compounds can be considered as a potential agent for the treatment of Alzheimer's diseases and diabetes mellitus.     

Description of excited states in [Re(Imidazole)(CO)3(Phen)]+ including solvent and spin‐orbit coupling effects: Density functional theory versus multiconfigurational wavefunction approach

The low‐lying electronic excited states of [Re(imidazole)(CO)₃(phen)]⁺ (phen = 1,10‐phenanthroline) ranging between 420 nm and 330 nm have been calculated by means of relativistic spin‐orbit time‐dependent density functional theory (TD‐DFT) and wavefunction approaches (state‐average‐CASSCF/CASPT2). A direct comparison between the theoretical absorption spectra obtained with different methods including SOC and solvent corrections for water points to the difficulties at describing on the same footing the bands generated by metal‐to‐ligand charge transfer (MLCT), intraligand (IL) transition, and ligand‐to‐Ligand‐ charge transfer (LLCT). While TD‐DFT and three‐roots‐state‐average CASSCF (10,10) reproduce rather well the lowest broad MLCT band observed in the experimental spectrum between 420 nm and 330 nm, more flexible wavefunctions enlarged either by the number of roots or by the number of active orbitals and electrons destabilize the MLCT states by introducing IL and LLCT character in the lowest part of the absorption spectrum. © 2016 Wiley Periodicals, Inc.     

Comparative theoretical study of the electron affinities of the alkaline‐earth clusters: Ben,Mgn, and Can (n = 2, 3)

If in atoms only one type of the electron affinity (EA) can be defined, in molecules there are three types of EAs: the vertical electron affinity (VEA), adiabatic electron affinity (AEA), and vertical electron detachment energy (VEDE). These three types of EAs for beryllium, magnesium, and calcium dimers and trimers are calculated at the all‐electron MP4(SDTQ) level employing the Dunning‐type basis sets. All obtained EAs satisfy the following inequality VEDE > AEA > VEA and are quite large to be observed in experiment, especially in the trimer case: VEDE (Be) = 1.63 eV, VEDE (Mg) = 0.72 eV, and VEDE (Ca) = 0.95 eV. The decomposition of VEDE into physical components (Koopmans, relaxation, and correlation) and the atomic orbital population analysis (at the NBO level) are used to elucidate the nature of the outer electron binding in studied anions. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Stereoselective Total Synthesis of Iso‐Cladospolide B and the 12 Membered‐Macrolactone (6S,12R)‐6‐Hydroxy‐12‐methyloxacyclododecane‐2,5‐dione

Total syntheses of iso‐cladospolide B ( 1 ) and the 12‐membered macrolactone (6S,12R)‐6‐hydroxy‐12‐methyloxacyclododecane‐2,5‐dione ( 2 ), a non‐natural product, were achieved from a common intermediate starting from commercially available 1,9‐nonane diol.     

Bridging gold: B‐Au‐B three‐center‐two‐electron bonds in electron‐deficient B2Aun−/0 (n = 1, 3, 5) and mixed analogues

A systematic density functional theory and wave function theory investigation on the geometrical and electronic structures of the electron‐deficient diboron aurides B₂Au (n = 1, 3, 5) and their mixed analogues B₂H_mAu (m + n = 3, 5) has been performed in this work. Ab initio theoretical evidences strongly suggest that bridging gold atoms exist in the ground states of C_2v B₂Au^?(¹A₁), C₂ B₂Au(¹A), C_2v B₂Au₃(²B₁), C_2v B₂Au(¹A₁), and C_s B₂Au₅(²A″), which all prove to possess a B? Au? B three‐center‐two‐electron (3c‐2e) bond. For B₂H_mAu (m + n = 3, 5) mixed anions, bridging B? Au? B units appear to be favored in energy over bridging B? H? B, as demonstrated by the fact that the Au‐bridged C_2v B₂H₂Au^? (¹A₁), C_s B₂HAu (¹A′), and C₁ B₂HAu (¹A) lie clearly lower than their H‐bridged counterparts C_s B₂H₂Au^? (¹A′), C₂ B₂HAu (¹A), and C_2v B₂HAu (¹A₁), respectively. Orbital analyses indicate that Au 6s makes about 92–96% contribution to the Au‐based orbitals in these B‐Au‐B 3c‐2e interactions, whereas Au 5d contributes 8–4%. The adiabatic and vertical detachment energies of the concerned anions have been calculated to facilitate their future experimental characterizations. The results obtained in this work establish an interesting 3c‐2e bonding model (B? Au? B) for electron‐deficient systems in which Au 6s plays a major role with non‐negligible contribution from Au 5d. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011