Chemistry Reference
In-Depth Information
Figure 4.13. STM images at the liquid/HOPG interface. (a) A ML of a
trans
-bis-
cyanoethylthio-bis-octadecylthio-TTF deposited from 1-octanol (10
10 nm
2
,
×
I
t
=
226 V). (b) A ML of a
trans
-bis-cyanoethylthio-bis-
octadecylthio-TTF deposited from 1-octanol (19
0
.
5 nA,
V
t
=−
0
.
5nm
2
,
I
t
=
.
5
×
19
.
0
.
5 nA,
V
t
=−
294 V) showing the two different polymorphs. (c) Zoom-in on the area
indicated in (b). Dark grey and white arrows indicate double-core and single-core
lamellae, respectively. Nine molecules are superimposed on the image for clarity
(9
0
.
9nm
2
,
I
t
=
×
0
.
5 nA,
V
t
=−
0
.
294 V). (d) A ML of
cis
-bis-cyanoethylthio-
.
×
.
8nm
2
,
I
t
=
.
9 nA,
V
t
=−
.
bis-octadecylthio-TTF (13
31 V). No single-
core lamellae are observed. Alkyl chains are interdigitating. (e) ML of
cis
-bis-
cyanoethylthio-bis-octadecylthio-TTF with superimposed molecules for clarity
(6
8
13
0
0
288 V). Gomar-Nadal
et al.
, 2003. Repro-
duced by permission of the Royal Society of Chemistry.
.
9
×
6
.
9nm
2
,
I
t
=
0
.
8 nA,
V
t
=−
0
.
single-core (white arrows) lamellae. In addition, the octadecyl chains are perpen-
dicular with respect to the lamellar axes and are interdigitating. The TTF cores
form an angle of 27
◦
with respect to the lamellar axis. The intermolecular distance
between equivalent molecules in a lamella is 1.52 nm. The alternation between
double and single rows can be explained as a result of the constraints imposed
by the alkyl chains in order to form a dense 2D packing with optimized van der
Waals interactions between the alkyl chains. In a double-core lamella (as is the
case with the first polymorph) the cyanoethyl groups cannot fully adsorb on the
