Design of Small Intramolecular Singlet Fission Chromophores: An Azaborine Candidate and General Small Size Effects

We report the first attempt to design small <i>intra</i>molecular singlet fission chromophores, with the aid of quantum chemistry and explicitly simulating the time evolution of state populations using quantum dynamics method. We start with three previously proposed azaborine-substituted <i>inter</i>molecular singlet fission chromophores. Through analyzing their frontier orbital amplitudes, we select a BN-substituted azulene as the building block. Covalently connecting two such monomers and tuning their relative configuration, we examine three dimers. One dimer is found to be an eminent candidate: the triplet-pair state is quickly formed within 1 ps, and the two triplets are ready to be disentangled. We elucidate the general small size effects in intramolecular singlet fission and focus on specific aspects which should be taken care of when manipulating the fission rate through steric hindrance

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23 septembre 19341934/09/23 (A63).Appartient à l’ensemble documentaire : PoitouCh

The Low-Lying Electronic States of Pentacene and Their Roles in Singlet Fission

We present a detailed study of pentacene monomer and dimer that serves to reconcile extant views of its singlet fission. We obtain the correct ordering of singlet excited-state energy levels in a pentacene molecule (<i>E</i> (<i>S</i>₁) < <i>E</i> (<i>D</i>)) from multireference calculations with an appropriate active orbital space and dynamical correlation being incorporated. In order to understand the mechanism of singlet fission in pentacene, we use a well-developed diabatization scheme to characterize the six low-lying singlet states of a pentacene dimer that approximates the unit cell structure of crystalline pentacene. The local, single-excitonic diabats are not directly coupled with the important multiexcitonic state but rather mix through their mutual couplings with one of the charge-transfer configurations. We analyze the mixing of diabats as a function of monomer separation and pentacene rotation. By defining an oscillator strength measure of the coherent population of the multiexcitonic diabat, essential to singlet fission, we find this population can, in principle, be increased by small compression along a specific crystal direction

Seeking Small Molecules for Singlet Fission: A Heteroatom Substitution Strategy

We design theoretically small molecule candidates for singlet fission chromophores, aiming to achieve a balance between sufficient diradical character and kinetic persistence. We develop a perturbation strategy based on the captodative effect to introduce diradical character into small π-systems. Specifically, this can be accomplished by replacing pairs of not necessarily adjacent C atoms with isoelectronic and isosteric pairs of B and N atoms. Three rules of thumb emerge from our studies to aid further design: (i) Lewis structures provide insight into likely diradical character; (ii) formal radical centers of the diradical must be well-separated; (iii) stabilization of radical centers by a donor (N) and an acceptor (B) is essential. Following the rules, we propose candidate molecules. Employing reliable multireference calculations for excited states, we identify three likely candidate molecules for SF chromophores. These include a benzene, a napthalene, and an azulene, where four C atoms are replaced by a pair of B and a pair of N atoms

Gene ontology (GO) analysis of differentially expressed proteins.

<p>GO annotations are presented by category: A) biological process B) cellular components C) molecular function.</p

2-DE patterns of proteins extracted from dairy goat liver.

<p>A. Control group; B. High-grain diet group. Fifty-two differentially expressed proteins showing significant spot intensity changes are marked in A and B. The proteins to which these 52 differentially expressed protein spots correspond are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080698#pone-0080698-t002" target="_blank">Table 2</a>.</p

Identification of differentially expressed liver proteins.

a<p>Numbering corresponds to the 2-DE gel in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080698#pone-0080698-g001" target="_blank">Fig.1</a>.</p>b<p>The total number of identified peptide.</p>c<p>Increased(>) or decreased(<) compared with the control group.</p

The primer sequences used for quantitative qRT-PCR of the differentially expressed genes related to diet type.

<p>The primer sequences used for quantitative qRT-PCR of the differentially expressed genes related to diet type.</p

Western blot analysis of calreticulin (CALR; A) and apolipoprotein A-I (ApoA-I; B) in liver tissue samples from high-grain diet and control groups.

<p>Protein extracts of liver tissue samples were prepared and subjected to immunodetection with the indicated antibodies. Intensities of CALR and ApoA-I bands were normalized to the corresponding β-actin control. Values are presented as means ± SD; n = 5. * <i>P</i><0.05.</p

KEGG pathway analysis of differentially expressed proteins.

<p>Pathway enrichment analysis was performed using the DAVID web application.</p