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2,5‐Disubstituted N,N′ ‐Dicyanobenzoquinonediimines (DCNQIs): Charge‐Transfer Complexes and Radical‐Anion Salts and Copper Salts with Ligand Alloys: Syntheses, Structures and Conductivities
Author(s) -
Hünig Siegfried,
Kemmer Martina,
Meixner Hubert,
Sinzger Klaus,
Wenner Hermann,
Bauer Thomas,
Tillmanns Ekkehart,
Lux Franz Rudolf,
Hollstein Michael,
Groß HansGeorg,
Langohr Uwe,
Werner HansPeter,
von Schütz Jost Ulrich,
Wolf HansChristoph
Publication year - 1999
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199905)1999:5<899::aid-ejic899>3.0.co;2-r
Subject(s) - chemistry , copper , ligand (biochemistry) , ion , charge (physics) , radical ion , inorganic chemistry , polymer chemistry , organic chemistry , biochemistry , receptor , physics , quantum mechanics
The new members of the series of 2,5‐disubstituted DCNQIs, 1d (Cl/OMe), 1e (Br/OMe), 1j (Cl/I), 1k (Br/I), 1l (I/I), form conducting charge‐transfer complexes with TTF (tetrathiofulvalene) which are comparable to known DCNQI/TTFs. From these DCNQIs highly conducting radical‐anion salts [2‐X, 5‐Y‐DCNQI] 2 M (M = Li, Na, K, NH 4 , Tl, Rb, Ag, Cu) can also be prepared either from the DCNQIs and MI (not AgI), on a metal wire (Ag, Cu), or by electrocrystallization (M = Tl, Ag,Cu). For better crystals a method using periodical switching between reduction and partial oxidation has been developed. With CF 3 (large, strongly electron‐attracting) as the substituent in DCNQIs 1m (OMe/CF 3 ) and 1n (Me/CF 3 ), conducting TTF complexes remain whereas only 1n yields an insulating copper salt. DCNQI–Cu salts with high conductivities are obtained with alloys containing two or three different DCNQIs. The temperature‐dependent conductivities of DCNQI–M salts (other than copper) are similar to those of metal‐like semiconductors. All new DCNQI–Cu salts are metallic [M] down to low temperatures, except [ 1d (Cl/OMe)] 2 Cu which undergoes a sharp phase transition to an insulating state[M → I]. By variation of the ligands or their ratios in conducting alloys of DCNQI–Cu salts temperature‐dependent conductivities can be tuned from M → I to M. In addition, alloying three ligands produced for the first time a radical salt with temperature‐independent conductivity from 5 to 300 K. Most remarkably, alloys of the type [(2,5‐Me 2 DCNQI) m ] Cu/[{2,5‐(CD 3 ) 2 ‐DCNQI} n ] 2 Cu which exhibit a sharp M → I phase transition on further cooling reenter the conducting state by an I → M transition, with changes of ca. 10 8 Scm −1 both ways. For the first time in the field of organic metals crystal structures of DCNQI–copper salts have been determined by X‐ray powder diffraction methods and refined by Rietveld analysis. Unit cell data, coordination angles and distances of the π planes are in excellent agreement with the single‐crystal X‐ray data. However, bond lengths and angles of the ligands are to be less accurate. This powder method proves to be most valuable if only microcrystalline material is available.