Ethylenedithiotetrathiafulvalene (EDTâTTF)
derivatives1â4 functionalised with a single
aromatic ring have been synthesised and their LangmuirâBlodgett (LB)
films have been assembled utilising only 25% molar ratio of fatty acid.
For compounds 1, 3 and 4, predominantly Y-type
deposition onto solid supports was observed with a transfer ratio close to
unity. After doping with iodine vapour, the maximum in-plane conductivity
values obtained were Ï
rt
=10
-3
S
cm
-1
for 1 and 3, and
10
-5
S cm
-1
for 4. LB
deposition of 2 was not uniform and the conductivity value after
doping was low. UVâVIS spectra of the LB films reveal the appearance
of a charge-transfer (CT) band at
λ
max
=ca. 900 nm for 1 and
4 after iodine doping. A solution of compound 3
exhibited a weak absorption band at ca. 665 nm which is assigned
to an intramolecular CT band; the intensity of this band increases on
exposure of the solution to light. This band is not observed in LB films
of 3, neither as-deposited nor after doping. Molecular orbital
calculations indicate that in the minimum energy conformation of
3, the pyridinium moiety is practically orthogonal to the TTF
unit and this conformation may be obtained in solution, enabling
charge-transfer to occur. A more linear conformation of 3 in the
LB films may prevent intramolecular charge-transfer from occurring.
Monolayers of 1, 3 and 4 were characterised by
cyclic voltammetry which revealed two redox steps consistent with the
formation of the EDTâTTF cation radical and dication,
respectively.
我们合成了具有单个芳香环功能的亚乙基二
硫代四
硫杂
戊烯(EDTâ
TTF)衍
生物1â4,并利用仅 25% 摩尔比的
脂肪酸组装了它们的朗缪尔-布洛杰特(LB)薄膜。 对于化合物 1、3 和 4,在固体支撑物上观察到的主要是 Y 型沉积,转移比接近于一。在掺入
碘蒸气后,1 和 3 获得的最大面内电导率值为 Ï rt =10 -3 S cm -1 ,4 为 10 -5 S cm -1 。2 的枸杞沉积不均匀,掺杂后的电导率值较低。枸杞薄膜的紫外可见光谱显示,1 和 4 在δ" max =ca.900 nm 处出现电荷转移(CT)带。化合物 3 的溶液在约 665 纳米波长处显示出一条微弱的吸收带。该吸收带的强度在溶液暴露于光线时会增加。在 3 的枸杞薄膜中,无论是沉积时还是掺杂后,都没有观察到这条带。分子轨道计算表明,在 3 的最小能量构象中,
吡啶鎓分子实际上与
TTF 单元正交,这种构象可以在溶液中获得,从而实现电荷转移。通过循环伏安法对 1、3 和 4 的单层膜进行了表征,发现其中有两个
氧化还原步骤分别与 EDTâ
TTF 阳离子自由基和二阳离子的形成相一致。