Carbonyl mediated conductance through metal bound peptides: a computational study

Large increases in the conductance of peptides upon binding to metal ions have recently been reported experimentally. The mechanism of the conductance switching is examined computationally. It is suggested that oxidation of the metal ion occurs after binding to the peptide. This is caused by the bias potential placed across the metal–peptide complex. A combination of configurational changes, metal ion involvement and interactions between carbonyl group oxygen atoms and the gold leads are all shown to be necessary for the large improvement in the conductance seen experimentally. Differences in the molecular orbitals of the nickel and copper complexes are noted and serve to explain the variation of the improvement in conductance upon binding to either a nickel or copper ion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58137/2/nano7_42_424003.pd

Bias effects on the electronic spectrum of a molecular bridge

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98651/1/JChemPhys_134_054708.pd

Benchmarking the performance of density functional theory based Green’s function formalism utilizing different self-energy models in calculating electronic transmission through molecular systems

Electronic transmission through a metal-molecule-metal system is calculated by employing a Green’s function formalism in the scattering based scheme. Self-energy models representing the bulk and the potential bias are used to describe electron transport through the molecular system. Different self-energies can be defined by varying the partition between device and bulk regions of the metal-molecule-metal model system. In addition, the self-energies are calculated with different representations of the bulk through its Green’s function. In this work, the dependence of the calculated transmission on varying the self-energy subspaces is benchmarked. The calculated transmission is monitored with respect to the different choices defining the self-energy model. In this report, we focus on one-dimensional model systems with electronic structures calculated at the density functional level of theory.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87873/2/204717_1.pd

Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design

Controlling the Emissive Activity in Heterocyclic Systems Bearing CP Bonds

The photophysical properties of a series of heteroatom substituted indoles are explored to identify chemical means to control their emissive activity. In particular, we consider impacts of changes in the conjugated backbone, where the CN bonds of benzoxazoles are replaced by CP bonds (benzoxaphospholes). The effects of extending the π-conjugation, incorporating various secondary heteroatoms (X–CP), and enforcing planar rigidity are also examined. Our computational analysis explains the higher fluorescence efficiency observed with extended π-conjugation and highlights the importance of maintaining molecular planarity at both ground- and emissive-state geometries

Calculating Off-Site Excitations in Symmetric Donor–Acceptor Systems via Time-Dependent Density Functional Theory with Range-Separated Density Functionals

Time-dependent density functional theory with range-separated hybrid functionals is used to calculate off-site excitations involving transitions between spatially separated orbitals in weakly coupled systems. Although such off-site excitations involve charge transfer, orbital degeneracy in symmetrical systems results in linear combinations of off-site excitations with equal weights and therefore zero net charge-transfer character. Like other types of off-site excitations, such “hidden” charge-transfer excitations are not accurately captured by conventional density functionals. We show that the recently introduced Baer–Neuhauser–Livshitz range-separated hybrid functional accurately characterizes such hidden off-site excitation energies via applications to the ethene dimer model system and to dye-functionalized silsesquioxanes