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The reaction of N,O-donor ligands hippuric acid and N-phenylanthranilic acid with [PtCl???(COD)] (COD = 1,5-cyclooctadiene) in dichloromethane and in the presence of silver(I) oxide yields the complexes [Pt{OC(O)CH???N(COPh)}(COD)] and [Pt{OC(O)(C???H???)N(Ph)}(COD)]. Several ligand-substitution reactions were performed using complex [Pt{OC(O)CH???N(COPh)}(COD)] and a variety of phosphines, to produce [Pt{OC(O)CH???N(COPh)}(PPh???)???].1.5.CH???Cl???, [Pt{OC(O)CH???N(COPh)}(dppe)][dppe = 1,2-bis(diphenylphosphino)ethane], [Pt{OC(O)CH???N(COPh)}(PTA)???] (PTA = 1,3,5-triaza-7-phosphaadamantane) and [Pt{OC(O)CH???N(COPh)}(dppf)] [1,1???-bis(diphenylphosphino)ferrocene]. The X-ray crystal structure of [Pt{OC(O)CH???N(COPh)}(COD)] was obtained which showed the hippurate ligand coordinated to platinum via the nitrogen and oxygen atoms. Atte...
This thesis reports the synthesis and characterisation of eight new platinum thiourea complexes. Thiourea dianion complexes of the type (Ph???P)???PtSC(=NR)NPh, R=Me, Et, Pr???, Pr???, Bu??? and (Ph???P)???PtSC(=NPh)NR R=Bu?? , p-tol, and the thiourea monoanion complex of the type [(Ph???P)???PtSC(=NEtH)NPh]??? were synthesised. This research confirms the prediction made by Henderson et al that asymmetrically substituted thiourea dianion complexes could form isomers. NMR studies show that the kinetically favoured isomer is formed initially, and then undergoes a solution phase isomerisation process to form the thermodynamically favoured isomer. Evidence that this isomerisation is affected by difference in substituent size and the energy difference between the two structures was obtained both experimentally, by use of NMR spectroscopy te...
The equilibrium geometry of the lowest energy structure of water dimer [(H₂O)₂] has been investigated using coupled cluster theory. A hierarchy of conventional coupled cluster methods is utilized up to singles doubles triples and quadruples excitations (CCSDTQ). The geometry of (H₂O)₂ is also optimized using the explicitly correlated coupled cluster singles doubles and perturbative triples [CCSD(T)-F12b] method. Overall, we find that the effect of including excitations beyond CCSD(T) is smaller than inclusion of core-valence correlation and comparable to scalar-relativistic and adiabatic effects.
We have calculated XH-stretching (where X=O, C, F, Cl) fundamental and overtone transitions for three diatomics and a few small molecules using a local mode model. The potential energy curves and dipole moment functions are calculated using the recently developed explicitly correlated coupled cluster with single doubles and perturbative triples theory [CCSD_T_-F12] with the associated VXZ-F12 (where X=D, T, Q) basis sets. We find that the basis set convergence of calculated frequencies and oscillator strengths obtained with the explicitly correlated method is much more rapid than with conventional CCSD(T) and the Dunning type correlation consistent basis sets. Furthermore, CCSD(T)-F12 frequencies and oscillator strengths obtained with the VTZ-F12 and VQZ-F12 basis sets are found to be in excellent agreement with the CCSD(T) complete ba...
We have optimized the geometry and calculated interaction energies for over 100 different complexes of CO₂ with various combinations of electron accepting (Lewis acid) and electron donating (Lewis base) molecules. We have used the recently developed explicitly correlated coupled cluster singles doubles and perturbative triples [CCSD(T)-F12] methods and the associated VXZ-F12 (where X = D,T,Q) basis sets. We observe only modest changes in the geometric parameters of CO₂ upon complexation, which suggests that the geometry of CO₂ adsorbed in a nanoporous material should be similar to that of CO₂ in gas phase. When CO₂ forms a complex with two Lewis acids via the two electron rich terminal oxygen atoms, the interaction energy is less than twice what would be expected for the same complex involving a single Lewis acid. We consider a seri...
We have investigated the slipped parallel and t-shaped structures of carbon dioxide dimer [(CO₂)₂] using both conventional and explicitly correlated coupled cluster methods, inclusive and exclusive of counterpoise (CP) correction. We have determined the geometry of both structures with conventional coupled cluster singles doubles and perturbative triples theory [CCSD(T)] and explicitly correlated cluster singles doubles and perturbative triples theory [CCSD(T)-F12b] at the complete basis set (CBS) limits using custom optimization routines. Consistent with previous investigations, we find that the slipped parallel structure corresponds to the global minimum and is 1.09 kJ mol⁻¹ lower in energy. For a given cardinal number, the optimized geometries and interaction energies of (CO₂)₂ obtained with the explicitly correlated CCSD(T)-F12b me...
We have optimized the lowest energy structures and calculated interaction energies for the H2O–H2O, H2O–H2S, H2O–NH3, and H2O–PH3 dimers with the recently developed explicitly correlated CCSD(T)-F12 methods and the associated VXZ-F12 (where X=D,T,Q) basis sets. For a given cardinal number, we find that the results obtained with the CCSD(T)-F12 methods are much closer to the CCSD(T) complete basis set limit than the conventional CCSD(T) results. In general we find that CCSD(T)-F12 results obtained with the VTZ-F12 basis set are better than the conventional CCSD(T) results obtained with an aug-cc-pV5Z basis set. We also investigate two ways to reduce the effects of basis set superposition error with conventional CCSD(T), namely, the popular counterpoise correction and limiting diffuse basis functions to the heavy atoms only. We find that...
We have optimized the lowest energy structures and calculated interaction energies for the CO₂–Ar, CO₂–N₂, CO₂–CO, CO₂–H₂O, and CO₂–NH₃ dimers with the recently developed explicitly correlated coupled cluster singles doubles and perturbative triples [CCSD(T)]-F12 methods and the associated VXZ-F12 (where X = D,T,Q) basis sets. For a given cardinal number, we find that results obtained with the CCSD(T)-F12 methods are much closer to the CCSD(T) complete basis set limit than the conventional CCSD(T) results. The relatively modest increase in the computational cost between explicit and conventional CCSD(T) is more than compensated for by the impressive accuracy of the CCSD(T)-F12 method. We recommend use of the CCSD(T)-F12 methods in combination with the VXZ-F12 basis sets for the accurate determination of equilibrium geometries and inter...
We have used different computational methods, including B3LYP, CCSD(T)-F12 and CBS-QB3, to study and compare the addition–elimination reaction of the nitrate radical NO₃ with four sulfur-containing species relevant to atmospheric chemistry: hydrogen sulfide (H₂S), dimethyl sulfide [(CH₃)₂S], dimethyl sulfoxide [(CH3)₂SO] and sulfur dioxide (SO₂). We find that the reaction with (CH₃)₂SO to give NO₂ + (CH₃)₂SO₂ has a very low barrier, and is likely to be the dominant oxidation mechanism for (CH₃)₂SO in the atmosphere. In agreement with previous experimental data and computational results, we find that the reaction with H₂S and SO₂ is very slow, and the reaction with (CH₃)₂S is not competitive with the hydrogen abstraction route. The differences in reaction energetics and rates between the four species are explained in terms of stabilizin...
We have identified the dimethylamine-trimethylamine complex (DMA-TMA) at room temperature in the gas phase. The Fourier transform infrared (FTIR) spectrum of DMA-TMA in the NH-stretching fundamental region was obtained by spectral subtraction of spectra of each monomer. Explicitly correlated coupled cluster calculations were used to determine the minimum energy structure and interaction energy of DMA-TMA. Frequencies and intensities of NH-stretching transitions were also calculated at this level of theory with an anharmonic oscillator local mode model. The fundamental NH-stretching intensity in DMA-TMA is calculated to be approximately 700 times larger than that of the DMA monomer. The measured and calculated intensity is used to determine a room temperature equilibrium constant of DMA-TMA of 1.7 × 10⁻³ atm⁻¹ at 298 K.
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