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.

Charge-Transfer Complexes

Mechanistic Aspects

Free-Radical Salts

Crystal-Structures

Solid Phase-Transformation

Magnetic-Properties

Redox Cycling Experiments

Electrical-Properties

Nucleation-Growth

TCNQ Microcrystals

Författare

J. Lu

Monash University

A. Nafady

King Saud University College of Science

Monash University

B.F. Abrahams

University of Melbourne

Muhammad Abdulhamid

Chalmers, Fysik, Kondenserade materiens fysik

B. Winther-Jensen

Monash University

Waseda 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

Mer information

Senast uppdaterat

2018-02-26