Structural, Spectroscopic, and Electrochemical Characterization of Semi-Conducting, Solvated [Pt(NH 3 ) 4 ](TCNQ) 2 ·(DMF) 2 and Non-Solvated [Pt(NH 3 ) 4 ](TCNQ) 2
Artikel i vetenskaplig tidskrift, 2017

© 2017 CSIRO. The demand for catalysts that are highly active and stable for electron-transfer reactions has been boosted by the discovery that [Pt(NH3)4](TCNQF4)2 (TCNQF4≤2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) is an efficient catalyst. In this work, we prepare and characterize the two related [Pt(NH3)4] 2+ complexes, [Pt(NH3)4](TCNQ)2·(DMF)2 (1) and [Pt(NH3)4] (TCNQ)2 (2). Reaction of [Pt(NH3)4](NO3)2 with LiTCNQ in a mixed solvent (methanol/dimethylformamide, 4:1v/v) gives [Pt(NH3)4] (TCNQ)2·(DMF)2 (1), whereas the same reaction in water affords [Pt(NH3)4](TCNQ)2 (2). 2 has been previously reported. Both 1 and 2 have now been characterized by single-crystal X-ray crystallography, Fourier-transform (FT)IR, Raman and UV-vis spectroscopy, and electrochemistry. Structurally, in 1, the TCNQ1-anions form infinite stacks with a separation between adjacent anions within the stack alternating between 3.12 and 3.42Å. The solvated structure 1 differs from the non-solvated form 2 in that pairs of TCNQ1-anions are clearly displaced from each other. The conductivities of pressed pellets of 1 and 2 are both in the semi-conducting range at room temperature. 2 can be electrochemically synthesized by reduction of a TCNQ-modified electrode in contact with an aqueous solution of [Pt(NH3)4] (NO3)2 via a nucleation growth mechanism. Interestingly, we discovered that 1 and 2 are not catalysts for the ferricyanide and thiosulfate reaction. Li+ and tetraalkylammonium salts of TCNQ1-/2-and TCNQF41-/2-were tested for potential catalytic activity towards ferricyanide and thiosulfate. Only TCNQF41-/2-salts were active, suggesting that the dianion redox level needs to be accessible for efficient catalytic activity and explaining why 1 and 2 are not good catalysts. Importantly, the origin of the catalytic activity of the highly active [Pt(NH3)4](TCNQF4)2 catalyst is now understood, enabling other families of catalysts to be developed for important electron-transfer reactions.

Mechanistic Aspects

TCNQ Microcrystals

Redox Cycling Experiments

Charge-Transfer Complexes

Solid Phase-Transformation

Crystal-Structures

Magnetic-Properties

Electrical-Properties

Free-Radical Salts

Nucleation-Growth

Författare

J. Lu

Monash University

A. Nafady

King Saud University College of Science

Monash University

B.F. Abrahams

University of Melbourne

Muhammad Abdelhamid

Chalmers, Fysik, Kondenserade materiens fysik

B. Winther-Jensen

Waseda University

Monash University

A.M. Bond

Monash University

L.L. Martin

Monash University

Australian Journal of Chemistry

0004-9425 (eISSN)

Vol. 70 9 997-1005

Ämneskategorier

Kemi

DOI

10.1071/CH17245

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Senast uppdaterat

2021-11-04