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Photoinduced charge separation in a Pt^II acetylide donor–acceptor triad based on 2-(1-pyrazole)-pyridine modified with naphthalene mono-imide electron acceptor

Lookup NU author(s): Dr Mohammed Alamiry

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Abstract

A class of molecular electron transfer cascades—those based on PtII complexes of 2-(1-pyrazole)-pyridine (pzpy) ligands—are reported. The synthesis of a new electron-acceptor imide-modified pzpy ligands is reported, and their application to transition-metal chemistry demonstrated by the synthesis of the PtII chloride and acetylide complexes. These donor–acceptor assemblies are promising models for investigation of photoinduced charge separation. Accordingly, picosecond time-resolved infrared (TRIR) and femtosecond transient absorption (TA) studies have been undertaken to elucidate the nature and dynamics of the lowest excited states in Pt(NAP-pyr-pyrazole)(–CC–Ph–C7H15)2. It has been established that the initial population of an MLL'CT excited state in the chromophoric [Pt(pyridine-pyrazole)(acetylide)] core is followed by an electron transfer to the naphthalimide (NAP) acceptor, forming a charge-separated state. This state is characterized by a large shift in ν(CO) vibrations of the NAP acceptor, as well as by a very intense and broad [×10 times in comparison to ν(CO)] asymmetric acetylide stretch which incorporates –CC–Pt–CC– framework and occurs at approximately 300 cm–1 lower in energy than its ground-state counterpart. In CH2Cl2 at room temperature, the charge-separated state with the lifetime of 150 ps collapses into an almost isoenergetic NAP-localized triplet state; the rate of this transformation changes upon decreasing the temperature to 263 K. This final excited state, 3NAP-(pyr-pyrazole)Pt(–CC–Ph–C7H15)2, has an unusually long, for PtII complexes, excited-state lifetime of tens of microseconds. The work demonstrates the possibility of tuning excited-state properties in this new class of PtII chromophores designed for electron-transfer cascades.

Publication metadata

Author(s): Sazanovich IV, Alamiry MAH, Meijer AJM, Towrie M, Davies S, Bennett RD, Weinstein JA

Publication type: Article

Publication status: Published

Journal: Pure and Applied Chemistry

Year: 2013

Volume: 85

Issue: 7

Pages: 1331-1348

Print publication date: 21/06/2013

ISSN (print): 0033-4545

ISSN (electronic): 1365-3075

Publisher: Walter de Gruyter GmbH & Co. KG

URL: http://dx.doi.org/10.1351/PAC-CON-13-04-02

DOI: 10.1351/PAC-CON-13-04-02

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