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Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor.

ABSTRACT: Constructing functional molecular systems for solar energy conversion and quantum information science requires a fundamental understanding of electron transfer in donor-bridge-acceptor (D-B-A) systems as well as competitive reaction pathways in acceptor-donor-acceptor (A-D-A) and acceptor-donor-acceptor' (A-D-A') systems. Herein we present a supramolecular complex comprising a tetracationic cyclophane having both phenyl-extended viologen (ExV²⁺) and dipyridylthiazolothiazole (TTz²⁺) electron acceptors doubly-linked by means of two p-xylylene linkers (TTzExVBox⁴⁺), which readily incorporates a perylene (Per) guest in its cavity (Per ⊂ TTzExVBox⁴⁺) to establish an A-D-A' system, in which the ExV²⁺ and TTz²⁺ units serve as competing electron acceptors with different reduction potentials. Photoexcitation of the Per guest yields both TTz⁺˙-Per⁺˙-ExV²⁺ and TTz²⁺-Per⁺˙-ExV⁺˙ in <1 ps, while back electron transfer in TTz²⁺-Per⁺˙-ExV⁺˙ proceeds via the unusual sequence TTz²⁺-Per⁺˙-ExV⁺˙ → TTz⁺˙-Per⁺˙-ExV²⁺ → TTz²⁺-Per-ExV²⁺. In addition, selective chemical reduction of TTz²⁺ gives Per ⊂ TTzExVBox³⁺˙, turning the complex into a D-B-A system in which photoexcitation of TTz⁺˙ results in the reaction sequence ²*TTz⁺˙-Per-ExV²⁺ → TTz²⁺-Per-ExV⁺˙ → TTz⁺˙-Per-ExV²⁺. Both reactions TTz²⁺-Per⁺˙-ExV⁺˙ → TTz⁺˙-Per⁺˙-ExV²⁺ and TTz²⁺-Per-ExV⁺˙ → TTz⁺˙-Per-ExV²⁺ occur with a (16 ± 1 ps)^-1 rate constant irrespective of whether the bridge molecule is Per⁺˙ or Per. These results are explained using the superexchange mechanism in which the ionic states of the perylene guest serve as virtual states in each case and demonstrate a novel supramolecular platform for studying the effects of bridge energetics within D-B-A systems.

SUBMITTER: Zhou J

PROVIDER: S-EPMC6471873 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor.

Zhou Jiawang J Wu Yilei Y Roy Indranil I Samanta Avik A Stoddart J Fraser JF Young Ryan M RM Wasielewski Michael R MR

Chemical science 20190311 15

Constructing functional molecular systems for solar energy conversion and quantum information science requires a fundamental understanding of electron transfer in donor-bridge-acceptor (D-B-A) systems as well as competitive reaction pathways in acceptor-donor-acceptor (A-D-A) and acceptor-donor-acceptor' (A-D-A') systems. Herein we present a supramolecular complex comprising a tetracationic cyclophane having both phenyl-extended viologen (ExV<sup>2+</sup>) and dipyridylthiazolothiazole (TTz<sup> ...[more]

PMID: 31057755

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Project description:During the last decades it has been established that breast cancer arises through the accumulation of genetic and epigenetic alterations in different cancer related genes. These alterations confer the tumor oncogenic abilities, which can be resumed as cancer hallmarks (CH). The purpose of this study was to establish the methylation profile of CpG sites located in cancer genes in breast tumors so as to infer their potential impact on 6 CH: i.e. sustained proliferative signaling, evasion of growth suppressors, resistance to cell death, induction of angiogenesis, genome instability and invasion and metastasis. For 51 breast carcinomas, MS-MLPA derived-methylation profiles of 81 CpG sites were converted into 6 CH profiles. CH profiles distribution was tested by different statistical methods and correlated with clinical-pathological data. Unsupervised Hierarchical Cluster Analysis revealed that CH profiles segregate in two main groups (bootstrapping 90-100%), which correlate with breast laterality (p = 0.05). For validating these observations, gene expression data was obtained by RealTime-PCR in a different cohort of 25 tumors and converted into CH profiles. This analyses confirmed the same clustering and a tendency of association with breast laterality (p = 0.15). In silico analyses on gene expression data from TCGA Breast dataset from left and right breast tumors showed that they differed significantly when data was previously converted into CH profiles (p = 0.033). We show here for the first time, that breast carcinomas arising on different sides of the body present differential cancer traits inferred from methylation and expression profiles. Our results indicate that by converting methylation or expression profiles in terms of Cancer Hallmarks, it would allow to uncover veiled associations with clinical features. These results contribute with a new finding to the better understanding of breast tumor behavior, and can moreover serve as proof of principle for other bilateral cancers like lung, testes or kidney.

Dataset Information

Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor.

Publications

Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor.

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