Phenalenyls, Cyclopentadienyls, and Other Carbon-Centered Radicals - Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds - page 121

(a)

(d)

(b)

(e)

(c)

(f)

Figure3.45 IRtransmittanceofsinglecrystalsof(a) [PLY(O,N)] 2 + B − (R 1 ethyl),(b) [PLY(O,N)] 2 + B − (R 1 = = n-

butyl), and (c) [PLY(O,N)] 2 + B − (R 1

n-Hex) at the high temperature (solid lines) and low temperature (dotted
lines) states. The arrows indicate cut-off frequencies of the transmittance (

=

ω c ). Bistability of (d) IR transmittance

at 3 m, (e) conductivity, and (f) magnetic susceptibility, arising from the hysteretic phase transition in

[PLY(O,N)] 2 + B − (R 1

. 85 µ

n-butyl). The open circles represent the cooling part of the temperature cycle, and the
closedcirclesrepresenttheheatingpart.Thearrowsindicatethedirectionofthetemperaturesweep.

=

the temperature region does not attract attention in standard measurements for molecule-based magnetic
materials. Thus, these studies underscore the importance of magnetic measurements in the high temperature
range above room temperature. 59c These materials are applicable for information storage devices and

molecular memory. 41
Importantly, these boron complexes have high stabilities and do not form

-dimer structures in the
crystalline states in spite of the lack of bulky substituents on the phenalenyl skeletons. 61,62 The crystal
structures greatly depend on the kinds of alkyl substituents at the nitrogen atoms coordinating the metal ions,
and the phenalenyl moieties form the

σ

steps structures. The magnetic susceptibility
measurements of all metal complexes (except for [PLY(O,N)] 2 + B − (R 1

π dimer, π chains, and π

= cyclooctyl)) show relatively

weak antiferromagnetic intermolecular exchange interactions (1 / 10 ∼ 1 / 100) in comparison with TBPLY

( 2000 K). Extended H uckel theory (EHT) band structure calculations suggest that [PLY(O,N)] 2 + B −

(R 1

−

5 eV. However, the complex has
an activated conductivity. The conducting behavior of this class of zwitterionic radicals, including this
cyclohexyl derivative, is considered in terms of a “resonating valence bond theory”. 63,66
Extension from the bisphenalenyl to trisphenalenyl metal complexes having silicon 69 or germanium 69b
as central metals (shown below) is intriguing from the viewpoint of multistage redox ability and lowering

= cyclohexyl) shows 3-D metallic behavior with a bandwidth of ∼ 0 .