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Previous work was successful at delineating reaction pathways for the photoactivated synthesis of an amine, [CztBu(PyriPr)(NH2−PyriPr)], by double intramolecular C−H activation and functionalization via irradiating a metal(II) azido complex, [CztBu(PyriPr)2NiN3. The present work seeks to expand upon earlier research, and to substitute the metal with iron or cobalt, and to expand the study to photocatalyzed intermolecular C−H activation and functionalization of organic substrates. Density functional theory (DFT) – B3LYP/6-31+G(d') and APFD/Def2TZVP – and time-dependent density functional theory (TDDFT) were used to propose a detailed pathway comprised of intermediates of low, intermediate, or high spin multiplicity and photo-generated excited states for the reaction of the azido complex, [CztBu(PyriPr)2MN3] to form the amine complex [CztBu(PyriPr)M(NH2−PyriPr)], M = Co, Ni or Fe, and the intermediates along the reaction pathway. For applications on quantum computing, the photophysical properties of photoactive d8 nickel(II) complexes are modeled. Such systems take advantage of a two-level system pathway between ground to excited state electronic transitions and could be useful for the discovery of successful candidates for a room temperature qubit, the analogue of a classical computational bit. A modified organometallic model, inspired by a nitrogen vacancy selective intersystem crossing model in diamond, was developed to take advantage of the formation of excited states. Tanabe-Sugano diagrams predict areas where these excited states may relax via phosphorescent emission. Under Zeeman splitting, these transitions create the conditions required for a two-level system needed to design a functional organometallic qubit.

<p>Utilizing a genetic algorithm training of the atom dipole interaction model was performed to arrive at C,H, N, & O atomic polarizabilities that constitute a correction to semiempirical molecular polarizability calculations increasing the accuracy of these calculations to near parity with DFT at a fraction of the computational load.</p>

Indiana University-Purdue University Indianapolis (IUPUI) / Molecular polarizability plays a significant role in chemistry, biology, and medicine. Classical prediction of polarizability often relies on atomic-type specific polarizability optimized for training set molecules, which limits the calculations to systems of similar chemical environment. Although ab initio (AI) quantum mechanical (QM) methods are more transferable in predicting molecular polarizability, their high computational costs especially when used with large basis sets for obtaining quantitatively reliable results make them less practical. To obtain accurate QM polarizability in an efficient manner, we have developed a dual-level approach, where the polarizability (α) obtained from the efficient semiempirical QM (SE) method is corrected using a set of element-base atomic polarizabilities derived from the atomic dipole interaction model (ADIM) to reproduce the density functional theory (DFT) results. We have optimized the atomic polarizability correction parameters for CHON-containing systems using a small training set of molecules and tested the resulting SE-ADIM model on the neutral drug-like molecules in the QM7B database. SE-ADIM corrected AM1 showed substantial improvement with its relative percent error (RPE) compared to B3LYP reduced from 33.81% to 3.35%. To further test its robustness for larger molecules in broader chemical bonding situations, we applied this method to a collection of drug molecules from the e-Drug3D database. For the 1004 molecules tested, our SE-ADIM model, which only contains four empirical parameters, greatly reduces the RPE in AM1 polarizability relative to B3LYP from 26.8% to 2.9%. Error decomposition shows consistent improvements across molecules with diverse bond saturations, molecular sizes, and charge states. In addition, we have applied AlphaML, a promising machine learning (ML) technique for predicting molecular polarizability, to the e-Drug3D dataset to compare its performance with our SE-ADIM correction of AM1. We found SE-ADIM performs competitively with AlphaML bolstering our confidence in the value of our method. Errors distinct to AlphaML were also discovered. We found four molecules for which AlphaML predicts negative molecular polarizabilities, all of which were peroxides. In contrast, SE-ADIM has no such issue with these molecules or this chemical type. Finally, to improve performance of SE-ADIM when correcting AM1 molecular polarizability calculations for charged molecules, we introduce a charge dependent polarizability (CDP) enabled SE-ADIM. Training the CDP enabled SE-ADIM with a single additional parameter, B, we were able to reduce error in AM1 molecular polarizability calculations of charged molecules relative to B3LYP from 29.57% to 5.16%. By contrast, SE-ADIM without CDP corrected AM1 relative to B3LYP had an RPE of 8.56%. The most benefit of CDP was evident within negatively charged molecules where AM1 error relative to B3LYP fell from 32.20% to 3.77% while SE-ADIM without CDP enabled error for these same negative molecules was 10.06%.

En stor samling dimolekylära vätebindningar med formen A – H … B, där AH är en alkyn, alkohol eller tiol och B = [Br–, Cl–, NH3, HCN] beräknas och utvärderas med Kohn-Sham täthetsfunktionalteori tillsammans med bassetet m062x/6-311+g(2df.2p). Dessa komplex utvärderas även med en punktladdningsmodell (som använder samma metod och basset), där atomerna i vätebindningsmottagaren B byts ut mot laddningar som passats för att återskapa laddningsfördelningen runt molekylen, med målet att separera och isolera de elektrostatiska och polariserande energikomponenterna från de totala interaktionsenergierna. Med hjälp av detta tillvägagångssätt visade det sig att vätebindningars komplexeringsenergi (i.e. interaktionsenergin med energikostnaden för att deformera atomkärnornas rymdgeometri borttagen), oberoende av karaktären hos monomeren AH eller B, till stor del består av elektrostatik och polarisation, medan laddningsutbyte, dispersion, och andra resttermer endast utgör en liten del av den totala interaktionen. Fördelningen mellan elektrostatik och polarisation varierar beroende på typen av monomerer i vätebindningen, men deras summa, den resulterande punktladdningsenergin, korrelerar linjärt (ΔECompl = 0.85ΔEPC ) med R2 = 0.995 över energiomfånget 0 &lt; ΔECompl &lt; 50 kcal mol–1. Detta blir ännu mer anmärkningsvärt då inkluderingen av komplexeringsenergierna från halogenbindningar i samma korrelation inte förändrar korrelationskoefficienten avsevärt, vilket indikerar att båda bindningstyperna består av samma energikomponenter även då bindningarna i sig är väldigt olika. / A large set of dimeric hydrogen bonds of the type A – H … B, where AH is an alkyne, alcohol, or thiol and B = [Br–, Cl–, NH3, HCN]  are computed and evaluated using Kohn-Sham density functional theory together with the m062x/6-311+g(2df.2p) basis set. These complexes are also evaluated using a point charge (PC) approach (using the same method and basis set), where the atoms of the hydrogen bond acceptor B are substituted for charges that are optimized to reproduce the charge distribution of the molecule, with the purpose of separating and isolating the electrostatics- and polarization energy components of the interaction energies. Using this approach it was discovered that the complexation energy of hydrogen bonds (i.e.the interaction energy with the energy cost of nuclear deformation corrected for), independent on the nature of either monomer AH or B, are largely made up of electrostatics and polarization, while charge transfer, dispersion, and other rest terms only make up a small fraction of the total interaction. The composition of electrostatics and polarization vary depending on the type of monomers in the hydrogen bond, but their sum, the PC interaction energy, correlates linearly (ΔECompl = 0.85ΔEPC )  with R2 = 0.995 over an energy span of 0 &lt; ΔECompl &lt; 50 kcal mol–1. This is made even more remarkable by the inclusion of halogen bonded complexation energies in the same correlation without changing the correlation coefficient significantly, indicating that the two bond types are comprised of the same components even though they are remarkably different in origin.

Metallic films, in conjunction with biochemical-targeted probes, are expected to provide early diagnosis, targeted therapy and non-invasive monitoring for epidemiology applications [1-4]. The resonance wavelength peaks, both plasmonic and Wood-Rayleigh Anomalies (WRAs), in the scattering spectra are affected by the metallic architecture. As of today, much research has been devoted to extinction efficiency in the plasmonic region. However, Wood Rayleigh Anomalies (WRAs) typically occur at wavelengths associated with the periodic distance of the structures. A significant number of papers have already focused on the plasmonic region of the visible spectrum, but a less explored area of research was presented here; the desired resonance wavelength region was 400-500nm, corresponding to the WRA for the silver film with perforated hole with a periodic distance of 400nm. Simulations obtained from the discrete dipole approximation (DDA) method, show sharp spectral bands (either high or low scattering efficiencies) in both wavelength regions of the visible spectrum simulated from Ag film with cylindrical hole arrays. In addition, surprising results were obtained in the parallel scattering spectra, where the electric field is contained in the XY plane, when the angle between the metallic surface and the incident light was adjusted to 14 degrees; a bathochromic shift was observed for the WRA peak suggesting a hybrid resonance mode. Metallic films have the potential to be used in instrumental techniques for use as sensors, i.e. surface plasmon resonance affinity biosensors, but are not limited to such instrumental techniques. Although the research here was aimed towards affinity biosensors, other sensory designs can benefit from the optimized Ag film motifs. The intent of the study was to elucidate metal film motifs, when incorporated into instrumental analysis, allowing the quantification of genetic material in the visible region. Any research group that routinely benefits from quantification of various analytes in solution matrices will also benefit from this study, as there are a bewildering number of instrumental sensory methods and setups available.

This dissertation describes the implementation of the molecular electronic structure calculations with an implicit solvent model using coupled-cluster theory. The theory for and the implementation of the solvent reaction field method (SCRF) and the reference interaction site model (RISM) at the coupled-cluster singles and doubles (CCSD) are presented. In the SCRF model a solute molecule is placed in a spherical cavity, and the outer solvent is represented by a dielectric continuum, which is characterized by the dielectric constant of the solvent. The reaction field is introduced to the system by using the multipole moment expansion of the electronic structure of the solute molecule and the dielectric constant. The SCRF method has been used to calculate the conformational equilibrium and the rotational barriers of 1,2-dichloroethane in vacuum and in different solvents. The calculated results are compared with experimental values. In addition, the solvent effects on the energetics of the mechanism of nitration of benzene are reported using the implemented CCSD-SCRF model. The idea of RISM is to replace the reaction field in continuum models by a microscopic expression in terms of the site-site radial distribution functions between solute and solvent, which can be calculated from the RISM integral equations. The statistical solvent distribution around the solute is determined based on the electronic structure of the solute, while the electronic structure of solute is influenced by the surrounding solvent distribution. Therefore, the wave function and the RISM equations are solved self-consistently with CCSD. Pair correlation functions, partial atomic charges, and solvation free energies of water and N-methylacetamide are calculated in liquid water using proposed theory. Both the CC-SCRF and CC-RISM methods have been implemented in a developmental version of the Q-Chem 3.2 quantum chemistry package.

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