Efficient State-Specific Natural Orbital Based Equation of Motion Coupled Cluster Method for Core-Ionization Energies: Theory, Implementation, and Benchmark.

We have implemented a reduced-cost partial triples correction scheme to the equation of motion coupled cluster method for core-ionization energy based on state-specific natural orbitals. The second-order Algebraic Diagrammatic Construction (ADC) method is used to generate the state-specific natural orbital, which provides quicker convergence of the core-IP value with respect to the size of the virtual space than that observed in standard MP2-based natural orbitals. The error due to truncation of the virtual orbital can be reduced by using a perturbative correction.

Pair Natural Orbital Equation-of-Motion Coupled-Cluster Method for Core Binding Energies: Theory, Implementation, and Benchmark.

We present the theory and implementation of a lower scaling core-valence separated equation-of-motion coupled-cluster approach based on domain-based local pair natural orbitals for core binding energies. The accuracy of the new method has been compared with that of the standard equation-of-motion coupled-cluster method and experimentally measured results. The use of pair natural orbitals significantly reduces the computation cost and can be applied to large molecules.

Ultrafast Proton-Transfer Reaction in Phenol-(Ammonia) Clusters: An Molecular Dynamics Investigation.

The ability of phenol to transfer a proton to surrounding ammonia molecules in a phenol-(ammonia) cluster depends on the relative orientation of ammonia molecules, and a critical field of about 285 MV cm is essential along the O-H bond for the proton-transfer process. MD simulations reveal that the proton-transfer process from phenol to ammonia cluster is spontaneous when the cluster has at least eight ammonia molecules, and the proton-transfer event is almost instantaneous (about 20-120 fs). These simulations also reveal that the rate-determining step for the proton-transfer process is the reorganization of the solvent around the OH group.

Synthesis, Characterization, and Luminescence Studies of Gold(I) Complexes with PNP- and PNB-Based Ligand Systems.

The synthesis, X-ray crystal structures, and spectroscopic studies of a series of PPh2N(2,6-iPr2C6H3)PPh2 (PNP) and PPh2N(2,6-iPr2C6H3)BCy2 (PNB; Cy = cyclohexyl) based gold(I) complexes are presented herein. The gold(I) chloride complexes 2 and 6 were treated with AgSbF6 to yield the corresponding dimeric dinuclear Au(I) cation (3) and dimeric mononuclear Au(I) cation (7) with PNP and PNB systems, respectively. The molecular structure of 3 revealed the presence of a strong intramolecular aurophilic interaction with a Au···Au bond distance of 2.

Thermochromic and mechanochromic luminescence umpolung in isostructural metal-organic frameworks based on Cu6I6 clusters.

Two isostructural metal-organic framework (MOF) materials, namely, {[MeSi((3)Py)3]6(Cu6I6)}n (1) and {[ MeSi((3)Qy)3]6(Cu6I6)}n (2), featuring Cu6I6 clusters were synthesized from tridentate arylsilane ligands of the type MeSi((3)Py)3 ((3)Py = 3-pyridyl) and MeSi((3)Qy)3 ((3)Qy = 3-quinolyl), respectively. While the MOF 1 displays the usual thermochromism associated with traditional Cu4I4Py4 clusters, the MOF 2 shows (3)XLCT/(3)MLCT emission due to the Cu6I6 cluster core at both 298 and 77 K, albeit with some marginal variations in its emission wavelengths. Interestingly, an unusual reversal in the mechanochromic luminescent behavior was observed for these isostructural MOFs at 298 K wherein a pronounced blue-shifted high energy emission for 1 (from orange to yellowish-orange) and a red-shifted low-energy emission for 2 (from green to orange) were obtained upon grinding these samples.