Ionic Multi‐Component Complexes of Fullerenes: Structures and Magnetic Properties

Abstract

New ionic multi‐component complexes (TBPDA)₂·(C₆₀ ^•−)·(D⁺), where TBPDA is N,N,N′,N′‐tetrabenzyl‐p‐phenylenediamine and D is decamethylchromocene (Cp∗₂Cr, 1), decamethylcobaltocene (Cp∗₂Co, 2), and tetrakis(dimethylamino)ethylene (TDAE, 3). The presence of D⁺, C₆₀ ^•− and neutral TBPDA in 1–3 was proved by the IR and UV‐visible‐NIR spectra. D⁺ and C₆₀ ^•− form loose layers in 1 and 3 and are spatially separated by bulky TBPDA molecules. The EPR spectra of the complexes show single Lorentzian line with g=2.2526 and ΔH=215 mT (1), g=1.9999 and ΔH=6.7 mT (2), and g=2.0009 and ΔH of 2.93 mT (3) at RT. The EPR signal of 2 was attributed to C₆₀ ^•− (Cp∗₂Co⁺ is diamagnetic), whereas those in 1 and 3 to resonating signal between C₆₀ ^•− (g=1.9996–2.0000) and cations Cp∗₂Cr⁺ (1) or TDAE^•+ (3) due to indirect coupling. The EPR signals from 2 and 3 are split into two components below 50 and 60 K and the magnetic moments of 1–3 decrease below 50–100 K. Both effects are associated with the formation of field‐induced short‐range antiferromagnetically ordered clusters. It was shown that D⁺ cations do not noticeably affect the antiferromagnetic interaction of spins in 1–3 probably due to their isolation by benzyl groups of TBPDA.

Keywords:

• Fullerene
• metallocenes
• crystal engineering
• solid‐state structures
• IR and EPR spectroscopy
• magnetic properties

Acknowledgements

The work was partly supported by Grant‐in‐Aid Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan (152005019, and COE programs, the RFBR grant N 03‐03‐32699, the Russian Science Support Foundation and INTAS YSF 05‐109‐4653.