equiv.), piperidine or homopiperidine (1 equiv.), lithium car-
bonate (5 equiv.), and DMF (20 mL ) was stirred at 50 °C for
10 h. Water (200 mL ) was added to the reaction mixture. The
products were extracted with chloroform. After removal of
chloroform, the crude products were purified by silica gel
column chromatography using hexanes–ethyl acetate as eluent.
4-(Dimethylamino)pyridine (0.5 equiv.) was added to a solu-
tion of the 4-piperidinobenzaldehyde or 4-homopiperidinoben-
zaldehyde (1 equiv.) and malononitrile (1.5 equiv.) in methanol
(15 mL ). The reaction mixture was kept at room temperature
and the product precipitated from the solution. The yellow
product was collected by filtration and purified by recrystalliz-
ation from acetone–water.
(m, H
, CLCKH), 6.71 (dd, H
arom
(s, 3 H, –OCH ), 3.44 (m, 4 H, 2×CH ), 1.70 (m, 6 H,
), 6.50 (dd, H
), 3.90
arom
arom
3
2
3×CH ). Anal. calcd for C H FN O (288.32): C 66.66%,
16 17 2 2
H 5.94%, N 9.71%; Found: C 66.51%, H 5.95%, N 9.72%.
2
2-Fluoro-4-piperidinobenzylidenemalononitrile
Mp 124.2 °C. 1H-NMR (CDCl , 200 MHz): d (ppm)=8.24 (t,
1 H
arom
1 H
arom
Anal. calcd for C H FN (255.29): C 70.57%, H 5.53%, N
(5).
3
), 7.79 (s, 1 H, CLCKH), 6.67 (dd, 1 H
), 6.47 (dd,
arom
), 3.48 (m, 4 H, 2×CH ), 1.71 (m, 6 H, 3×CH ).
2
2
15 14
3
16.46%; Found: C 70.41%, H 5.44%, N 16.40%.
2,5-Difluoro-4-piperidinobenzylidenemalononitrile
(6).
Mp 139.5 °C. 1H-NMR (CDCl , 200 MHz): d (ppm)=8.00
3
2,3,5,6-Tetrafluoro-4-piperidinobenzaldehyde.
1H-NMR
(dd, 1 H
), 7.82 (s, 1 H, CLCKH), 6.60 (dd, 1 H
), 3.39
arom
(m, 4 H, 2×CH ), 1.71 (m, 6 H, 3×CH ). Anal. calcd for
arom
(CDCl , 200 MHz): d (ppm)=10.14 (s, 1 H, CHO), 3.38 (s, 4
3
2
2
H, 2×CH ), 1.72 (m, 6 H, 3×CH ).
C H F N (273.29): C 65.92%, H 4.79%, N 15.38%; Found:
2
2
15 13 2
3
C 65.81%, H 4.86%, N 15.34%.
2-Fluoro-4-piperidinobenzaldehyde.
1H-NMR
(CDCl ,
3
200 MHz): d (ppm)=10.03 (s, 1 H, CHO), 7.67 (t, 1 H
),
2,5-Difluoro-4-homopiperidinobenzylidenemalononitrile (7).
arom
), 3.38 (m, 4 H, 2×CH ),
6.64 (dd, 1 H
arom
1.66 (m, 6 H, 3×CH ).
), 6.44 (dd, 1 H
Mp 141.5 °C. 1H-NMR (CDCl , 200 MHz): d (ppm)=8.00
arom
2
3
(dd, 1 H
), 7.76 (s, 1 H, CLCKH), 6.42 (dd, 1 H
), 3.62
2
arom
(m, 4 H, 2×CH ), 1.84 (m, 4 H, 2×CH ), 1.62 (m, 4 H,
arom
2,5-Difluoro-4-piperidinobenzaldehyde. 1H-NMR (CDCl ,
2
2
3
2×CH ). Anal. calcd for C H F N (287.31): C 66.89%, H
200 MHz): d (ppm)=10.10 (d, 1 H, CHO), 7.44 (dd, 1 H
),
2
16 15 2 3
arom
), 3.27 (m, 4 H, 2×CH ), 1.78 (m, 6 H,
5.22%, N 14.63%; Found: C 66.88%, H 5.22%, N 14.63%.
6.54 (dd, 1 H
arom
2
3×CH ).
2
2,3,5,6-Tetrafluoro-4-
homopiperidinobenzylidenemalononitrile (8). Mp 104.5 °C. 1H-
2,5-Difluoro-4-homopiperidinobenzaldehyde.
1H-NMR
NMR (CDCl , 200 MHz): d (ppm)=7.63 (s, 1 H, CLCKH),
(CDCl , 200 MHz): d (ppm)=10.02 (d, 1 H, CHO), 7.43 (dd,
3
3
3.58 (m, 4 H, 2×CH ), 1.84 (m, 4 H, 2×CH ), 1.67 (m, 4 H,
1 H
), 6.40 (dd, 1 H
), 3.53 (m, 4 H, 2×CH ), 1.83 (m,
2
2
arom
arom
2
2×CH ). Anal. calcd for C H F N (323.29): C 59.45%, H
4.05%, N 13.00%; Found: C 59.21%, H 4.18%, N 12.88%.
4 H, 2×CH ), 1.65 (m, 4 H, 2×CH ).
2
16 13 4 3
2
2
2,3,5,6-Tetrafluoro-4-homopiperidinobenzaldehyde. 1H-NMR
2,3,5,6-Tetrafluoro-4-piperidinobenzylidenemalononitrile (9).
(CDCl , 200 MHz): d (ppm)=10.12 (s, 1 H, CHO), 3.57 (m,
3
Mp 112.5 °C. 1H-NMR (CDCl , 200 MHz): d (ppm)=7.65 (s,
4 H, 2×CH ), 1.82 (m, 4 H, 2×CH ), 1.67 (m, 4 H, 2×CH ).
3
2
2
2
1 H, CLCKH), 3.41 (m, 4 H, 2×CH ), 1.70 (m, 6 H, 3×CH ).
2
2
Anal. calcd for C H F N (309.27): C 58.26%, H 3.59%, N
13.59%; Found: C 58.36%, H 3.52%, N 13.53%.
4-Piperidinobenzaldehyde. 1H-NMR (CDCl , 200 MHz): d
15 11 4
3
3
(ppm)=9.74 (s, 1 H, CHO), 7.70 (d, 2 H
, J=8.9 Hz), 6.88
arom
(d, 2 H
arom
3×CH ).
, J=8.9 Hz), 3.40 (m, 4 H, 2×CH ), 1.67 (m, 6 H,
2
B Sample preparation
2
Photorefractive
PVK5ECZ5chromophore 25151 wt. ratio. TNFDM and C
were used at concentrations of 0.50 mg per 200 mg mix-
ture and 2 mg per 200 mg mixture, respectively. The
PVK–ECZ–TNFDM or
chromophore had a PVK5ECZ wt. ratio of 352, but identical
TNFDM and C concentrations to their photorefractive
counterparts.
For the sample preparation, PVK, ECZ, chromophore and
TNFDM were dissolved in anhydrous CH Cl . C was dis-
solved in toluene and added to the CH Cl solution. After
filtering through an AcrodiscA filter with 0.2 mm PTFE mem-
brane, the solvent was evaporated on a rotary evaporator.
The material was dried at 65 °C and 5 cm Hg for 2–6 h to
remove the residual solvent. The dried material was homogen-
ized mechanically at 150 °C. Small pieces of the homogenized
material were then sandwiched between ITO-coated glass slides
at 150 °C. 105 mm glass beads were used as spacers to ensure
samples
had
a
composition
of
60
4-Homopiperidinobenzaldehyde.
1H-NMR
(CDCl ,
3
200 MHz): d (ppm)=9.70 (s, 1 H, CHO), 7.71 (d, 2 H
,
arom
, J=8.9 Hz), 3.54 (m, 4 H,
J=8.9 Hz), 6.70 (d, 2 H
arom
2×CH ), 1.80 (m, 4 H, 2×CH ), 1.58 (m, 4 H, 2×CH ).
2
2
2
C
reference samples without
60
a-Cyano-4-piperidinocinnamic acid, methyl ester (1).
Mp 97.8 °C. 1H-NMR (CDCl , 200 MHz): d (ppm)=8.07 (s,
60
3
CLCKH), 7.90 (d, 2 H
, J=9.1 Hz), 6.85 (d, 2 H
, J=
arom
arom
9.1 Hz), 3.89 (s, 3 H, –OCH ), 3.47 (m, 4 H, 2×CH ), 1.68
3
2
(m, 6 H, 3×CH ). Anal. calcd for C H N O (270.33): C
2
2
60
2
16 18 2 2
71.09%, H 6.71%, N 10.36%; Found: C 71.12%, H 6.82%,
N 10.47%.
2
2
4-Homopiperidinobenzylidenemalononitrile (2). Mp 148.3 °C.
1H-NMR (CDCl , 200 MHz): d (ppm)=7.79 (d, 2 H
arom
, J=9.1 Hz),
, J=
3
9.1 Hz), 7.43 (s, 1 H, CLCKH), 7.71 (d, 2 H
arom
3.58 (t, 4 H, 2×CH ), 1.82 (m, 4 H, 2×CH ), 1.60 (m, 4 H,
2
2
2×CH ). Anal. calcd for C H N (251.33): C 76.46%, H
2
16 17 3
a
uniform sample thickness. The sample was then
6.82%, N 16.72%; Found: C 76.29%, H 6.90%, N 16.61%.
quench-cooled and sealed with epoxy glue.
The glass transition temperatures T of the TNFDM-based
materials were measured using the reversible heat flow compo-
nent in a Thermal Instruments 2920 m-DSC at an underlying
4-Piperidinobenzylidenemalononitrile (3). Mp 128.5 °C. 1H-
g
NMR (CDCl , 200 MHz): d (ppm)=7.77 (d, 2 H
, J=
3
arom
, J=9.1 Hz),
9.1 Hz), 7.44 (s, 1 H, CLCKH), 6.83 (d, 2 H
arom
3.49 (m, 4 H, 2×CH ), 1.71 (m, 6 H, 3×CH ). Anal. calcd
heating rate of 5 °C min−1 and a modulation of 0.796 °C
2
2
every 60 s. T values are reported in Table 1. Linear absorption
for C H N (237.29): C 75.93%, H 6.37%, N 17.71%; Found:
g
15 15
5
spectra of the different samples were measured with a Cary
C 75.74%, H 6.42%, N 17.62%.
5G spectrophotometer. In the sample, the polymer is sand-
wiched between two parallel ITO electrodes and due to mul-
tiple reflections at these interfaces, interference fringes are
a-Cyano-4-piperidino-2-fluorocinnamic acid, methyl ester (4).
Mp 138.5 °C. 1H-NMR (CDCl , 200 MHz): d (ppm)=8.40
3
2252
J. Mater. Chem., 1999, 9, 2251–2258