Minnesota Density Functionals

Transcription

1 Main Group Thermochemistry Minnesota Density Functionals D e 2 oncovalent Interactions M06-ass Functionals Long-range Charge Transfer Thermochemical Kinetics Transition Metal Chemistry We have developed the Minnesota density functionals, which are the most accurate density functionals with broad applicability in chemistry. See Y. Zhao and D. G. Truhlar, Theor. Chem. Acc. 120, 215 (2008), Acc. Chem. Res. 41, 157 (2008).

2 MUE (kcal/mol) MUE (kcal/mol) Default 274 data for aqueous neutrals 666 data for nonaqueous neutrals 112 data for aqueous ions 220 data for nonaqueous ions IEF-PCM/G03 CPCM/GAMESS COSMO/WChem SMD 274 data for aqueous neutrals 666 data for nonaqueous neutrals 112 data for aqueous ions 220 data for nonaqueous ions IEF-PCM/G03 CPCM/GAMESS COSMO/WChem The SMD Solvation Model We have developed a new charge-density-based solvation model called SMD. The algorithm used in SMD involves an integration of the nonhomogeneous Poisson equation for electrostatics. The SMD model has been parametrized using a large training set of neutral and ionic solvation free energies for various solutes in water and organic solvents (nearly 3000 data). The non-bulk-electrostatic part of the SMD model utilizes the cavity dispersion solvent-structure formalism that was worked out for previous solvation models developed at the. The figures demonstrate the significant improvement in the quality of IEFPCM/Gaussian 03, CPCM/GAMESS, and GCOSMO/WChem upon using the SMD parameters instead of the default settings for the current implementations of these models in Gaussian 03 (G03), GAMESS, and WChem (note: MUE stands for mean unsigned error, that is, mean absolute deviation from a set of accurate data). A. V. Marenich, C. J. Cramer, and D. G. Truhlar, J. ys. Chem. B 113, 6378 (2009)

3 Attractive oncovalent Interactions in the Mechanism of Grubbs Second-Generation Catalysts for Olefin Metathesis Second-generation ruthenium carbenoid catalysts for olefin metathesis are a hundred to a thousand times more active than first-generation catalysts, despite a slower initiation step. A new density functional capable of treating medium-range correlation energy shows that the relative rates of generation of the catalyst are determined by attractive noncovalent interactions. (1) BDE (1 ) + BDE(2) BDE (1) experiment +3.4 popular density functionals -2 to -1 new Minnesota functional +4 (2) BDE (2 ) + Y. Zhao and D. G. Truhlar, Org. Lett. 9, 1967 (2007)

4 C 60 C Size-Selective Supramolecular Chemistry in a Hydrocarbon anoring C 70 C (3,3) (3,3)@[6]CPPA (4,4) (4,4)@[6]CPPA (5,5) (5,5)@[6]CPPA ew-generation density functionals (M06-L and M06-2X) include an accurate treatment of medium-range correlation energy and have been applied to investigate host-guest interactions in supramolecular complexes in which a carbon nanoring, [6]paraphenyleneacetylene ([6]CPPA), acts as the host molecule. Guests include fullerenes and carbon nanotubes. The nature of the interactions has been discussed and analyzed. The size-selective supramolecular chemistry in the nanoring has been investigated by varying the size of the guest molecules and optimizing inclusion structures as large as C 128 H 44. We found that the (5,5) armchair-type nanotube fits in the [6]CPPA hydrocarbon nanoring better than the (3,3) or (4,4) ones, and C 70 is bound more strongly than C 60. Y. Zhao and D. G. Truhlar, J. Am. Chem. Soc. 129, 8440 (2007)

5 PL Hybrid Approach for Excited States and for Free Energy Calculations with High-Level Methods Evolution of the excited state energies of cytosine base in the native DA environment was investigated using a hybrid coupled cluster and classical molecular dynamics approach. The time-averaged excitation energies obtained with the variant of the completely renormalized equation-of-motion with singles, doubles, and noniterative triples approach that includes most of the correlation effects for excited states, are compared with the analogous calculations in the gas phase. M. Valiev and K. Kowalski, J. Chem. ys. 125, (2006); M. Valiev, B. C. Garrett, M.-K. Tsai, K. Kowalski, S. M. Kathmann, G. K. Schenter, and M. Dupuis, J. Chem. ys. 127, (2007) We also presented an approach to calculate the free energy profile along a condensed-phase reaction path based on high-level electronic structure methods for the reactive region. Most of statistical averaging is shifted toward less expensive descriptions by using a hierarchy of representations that includes molecular mechanics, density functional theory, and coupled cluster theories.

6 University of South Carolina Multiscale Model Development, Implementation, and Application Schematic representation of the adaptive partitioning molecular dynamics (AP-MD) method for a nanoparticle (blue spheres) or an oxide surface (grey, and red spheres) in contact c with a fluid phase (fluid molecules not shown). Low level of theory / low resolution anoparticle High level of theory / high resolution Fluid molecules close to the surface (within the light blue spheres) are treated during a molecular dynamics simulation at a high level of theory while fluid molecules away from the surface (outside the light blue spheres) are treated at a lower level of theory. Solid surface A. Heyden and D. G. Truhlar, J. Chem. Theory Comput. 4, 217 (2008)

7 Enzyme Catalysis: Quantum Effects and on-perfect Synchronization As a target for anti-cancer and anti-bacterial drugs, dihydrofolate reductase (DHFR) plays a critical role in maintaining the intracellular concentration of tetrahydrofolate (THF), an important reductive cofactor in biosynthesis of DA building blocks and several amino acids. The H/D kinetic isotope effects (KIEs) for the E. coli DHFRcatalyzed hydride transfer display an unusually small dependence on temperature, which is contrary to experience with small-molecule chemistry or simple tunneling models. Free energy simulations based on a combined QM/MM potential and KIE calculations employing ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT) indicated that the small temperature dependence results not from some intrinsically temperature-independent mechanism but rather from a near cancellation of competing temperature-dependent effects. The theoretical study also revealed an interesting non-perfect synchronization of reaction center rehybridizations during the hydride transfer, where the rehybridization of the hydride-acceptor carbon is significantly advanced compared to that of the hydride-donor carbon, resulting in a compressed transition state. J. Pu, S. Ma, M. Garcia-Viloca, J. Gao, D. G. Truhlar, and A. Kohen, J. Am. Chem. Soc. 127, (2005)