Compact All-Carbon Tripodal Tether
respect to the surface normal.8 Finally, we note that
attachment via three legs of the compact tripod and a
tilted orientation for the porphyrin are not inconsistent.
Molecular models of the tripod on the Si(100) surface
show that tilted orientations are possible owing to the
torsional flexibility of the alkane chains in the linker.
Regardless of the origin of the increased packing density
afforded by the compact tripod, this adsorption charac-
teristic has important consequences for molecular infor-
mation storage in that higher surface coverage results
in longer charge-retention times.
Cobalt(II)-5-[4-(4-allylhepta-1,6-dien-4-yl)phenyl]-10,-
15,20-tri-p-tolylporphyrin (Co-1). A solution of 1 (13.9 mg,
18 µmol) in CHCl3 (8.5 mL) was treated with a solution of Co-
(OAc)2 (31.1 mg, 176 µmol) in MeOH (1.7 mL) at room
temperature. The reaction mixture was refluxed for 8 h with
monitoring by TLC. The reaction mixture was concentrated
and then CH2Cl2 was added. The organic solution was washed
with water, dried (Na2SO4), concentrated, and chromato-
graphed [silica, hexanes/CH2Cl2 (2:1)] to afford a red solid (14
mg, 92%): 1H NMR δ 3.80-3.98 (m, 6H), 4.08-4.26 (br, 9H),
6.00-6.20 (m, 6H), 7.10-7.23 (br, 3H), 9.65-9.95 (m, 8H),
12.6-13.6 (br, 8H), 15.60-16.60 (br, 8H); MALDI-MS obsd
848.1; FABMS obsd 847.3267, calcd 847.3211 (C57H48CoN4);
λabs 413, 530 nm.
Experimental Section
4-(4-Allylhepta-1,6-dien-4-yl)aniline (3c). Following a
literature procedure carried out at the 2-mmol scale,12 a 2 M
solution of allylmagnesium chloride in THF (0.400 L, 0.800
mol) was diluted with additional THF (1.00 L) and then treated
dropwise with a solution of 4-(trifluoromethyl)aniline (19.9 mL,
0.160 mol) in THF (210 mL) at -50 °C under argon. After
complete addition the sides of the reaction flask were rinsed
with additional THF (150 mL). The resulting mixture was
heated at reflux. The reaction was monitored by TLC for the
complete consumption of 4-(trifluoromethyl)aniline. After 3.5
h, the mixture was concentrated and then CH2Cl2 was added.
The organic solution was washed with water, dried (Na2SO4),
and filtered. The filtrate was concentrated and chromato-
graphed [silica, CH2Cl2/hexanes (2:1)], affording a pale yellow
solid (31.7 g, 87%): 1H NMR δ 2.36-2.43 (m, 6H), 3.48-3.66
(br, 2H), 4.94-5.06 (m, 6H), 5.50-5.64 (m, 3H), 6.62-6.70 (m,
2H), 7.06-7.12 (m, 2H); 13C NMR δ 42.1, 42.6, 115.0, 117.5,
127.6, 135.0, 135.8, 144.1; FABMS obsd 228.1757, calcd
228.1752 [(M + H)+, M ) C16H21N].
1-(4-Allylhepta-1,6-dien-4-yl)-4-iodobenzene (4). A solu-
tion of concentrated HCl/H2O (1:1 v/v, 44 mL) was added to a
solution of 3c (11.4 g, 50.2 mmol) in THF (80 mL). The mixture
was stirred at room temperature for 75 min and then cooled
to 0-5 °C. A chilled solution of NaNO2 (7.99 g, 116 mmol) in
water (80 mL) was added while maintaining the temperature
of the reaction mixture below 5 °C. Additional H2O (30 mL)
was added. The reaction mixture was tested for the presence
of nitrous acid with KI-starch paper. A solution of KI (14.2 g,
85.5 mmol) in H2O (16 mL) cooled to ∼5 °C was added, again
maintaining the mixture at <5 °C throughout the addition.
Additional H2O (24 mL) and THF (150 mL) were added. The
reaction mixture was then gradually allowed to warm to room
temperature. After ∼6.5 h, the reaction mixture was neutral-
ized with saturated aqueous Na2CO3 and then filtered. The
filtrate was concentrated. The resulting residue was dissolved
in CH2Cl2 and washed with water. The organic phase was
dried (Na2SO4), concentrated, and chromatographed (silica,
hexanes) to afford a colorless liquid (4.73 g, 28%): 1H NMR
(300 MHz) δ 2.38-2.50 (m, 6H), 4.94-5.12 (m, 6H), 5.44-5.64
(m, 3H), 7.00-7.12 (m, 2H), 7.58-7.70 (m, 2H); 13C NMR δ
41.8, 42.0, 43.5, 91.4, 117.8, 118.2, 129.1, 134.2, 137.3, 145.8.
Synthesis. 5-[4-(4-Allylhepta-1,6-dien-4-yl)phenyl]-10,-
15,20-tri-p-tolylporphyrin (1). Following a general proce-
dure,17,18 a solution of 817 (0.42 g, 0.60 mmol) in THF/MeOH
(10:1, 24 mL) was treated with NaBH4 (0.91 g, 24 mmol) at
room temperature. After 2 h, the reaction mixture was
quenched with saturated aqueous NH4Cl and extracted with
CH2Cl2. The organic phase was dried (Na2SO4) and concen-
trated to provide the corresponding dicarbinol 8-diol. The
resulting dicarbinol was then immediately subjected to con-
densation with dipyrromethane 7 (214 mg, 0.600 mmol) in the
presence of Yb(OTf)3 (2.98 g, 4.81 mmol) in CH2Cl2 (240 mL).
After 80 min, DDQ (409 mg, 1.80 mmol) was added and the
mixture was stirred for 1 h. Then TEA (2.40 mL) was added
and the mixture was stirred for about 30 min. The reaction
mixture was passed through a pad of silica and eluted with
CH2Cl2. The porphyrin band was collected and chromato-
graphed [silica, hexanes/ethyl acetate (9:1 f 4:1)] to provide
a pink solid (139 mg, 29%): 1H NMR δ -2.75 (s, 2H), 2.65-
2.74 (m, 15H), 5.12-5.24 (m, 6H), 5.77-5.93 (m, 3H), 7.46-
7.60 (m, 6H), 7.65 (d, J ) 8.0 Hz, 2H), 8.04-8.12 (m, 6H), 8.14
(d, J ) 8.0 Hz, 2H), 8.76-8.83 (m, 2H), 8.83-8.92 (m, 6H);
MALDI-MS obsd 791.1; FABMS obsd 791.4146, calcd 791.4114
[(M + H)+, M ) C57H50N4]; λabs 421, 516, 551, 594, 649 nm.
Zinc(II)-5-[4-(4-allylhepta-1,6-dien-4-yl)phenyl]-10,15,-
20-tri-p-tolylporphyrin (Zn-1). A solution of 1 (131.8 mg,
167 µmol) in CHCl3 (13 mL) was treated with a solution of
Zn(OAc)2‚2H2O (183 mg, 0.832 mmol) in MeOH (2.6 mL) at
room temperature. The reaction was followed by TLC. The
reaction was complete in 2 h. The reaction mixture was washed
with saturated aqueous NH4Cl and extracted with CH2Cl2. The
combined organic layer was dried (Na2SO4), concentrated, and
chromatographed [silica, hexanes/ethyl acetate (9:1)] to afford
a pink solid (132 mg, 93%): 1H NMR δ 2.66-2.78 (m, 15H),
5.12-5.28 (m, 6H), 5.80-5.96 (m, 3H), 7.50-7.60 (m, 6H), 7.67
(d, J ) 8.4 Hz, 2H), 8.04-8.14 (m, 6H), 8.16 (d, J ) 8.4 Hz,
2H), 8.88-8.94 (m, 2H), 8.94-9.02 (m, 6H); MALDI-MS obsd
852.4; FABMS obsd 852.3193, calcd 852.3170 (C57H48N4Zn);
λabs 424, 551 nm.
Nickel(II)-5-[4-(4-allylhepta-1,6-dien-4-yl)phenyl]-10,-
15,20-tri-p-tolylporphyrin (Ni-1). A solution of 1 (12.3 mg,
15 µmol) in CHCl3 (1.9 mL) was treated with a solution of Ni-
(OAc)2‚4H2O (3.8 mg, 15 µmol) in MeOH (0.5 mL) at room
temperature. The reaction was followed by TLC. The reaction
did not proceed even after 9 h. Therefore, an additional portion
of Ni(OAc)2‚4H2O (85 mg, 0.34 mmol) in MeOH (4 mL) and
CHCl3 (16 mL) was added, and the reaction mixture was
refluxed. After 11 h, some free base porphyrin remained.
Another portion of Ni(OAc)2‚4H2O (8.0 mg, 32 µmol) in MeOH
(1 mL) was added and the reaction mixture was allowed to
reflux for another 2 h. The reaction mixture was concentrated
and then CH2Cl2 was added. The organic solution was washed
with water, dried (Na2SO4), concentrated, and chromato-
graphed [silica, hexanes/CH2Cl2 (2:1)] to afford a pink solid
(12 mg, 94%): 1H NMR δ 2.60-2.71 (m, 15H), 5.08-5.22 (m,
6H), 5.72-5.90 (m, 3H), 7.42-7.52 (m, 6H), 7.60 (d, J ) 8.4
Hz, 2H), 7.84-7.92 (m, 6H), 7.95 (d, J ) 8.4 Hz, 2H), 8.66-
8.82 (m, 8H); MALDI-MS obsd 847.2; FABMS obsd 846.3284,
calcd 846.3232 (C57H48N4Ni); λabs 417, 528 nm.
4-(4-Allylhepta-1,6-dien-4-yl)benzonitrile (5). Following
a literature procedure,24 a mixture of 4 (5.07 g, 15.0 mmol),
CuCN (2.03 g, 22.6 mmol) and DMF (50 mL) was heated over
the course of 30 min until refluxing was attained. The mixture
was refluxed for 3 h. The reaction was monitored by TLC. The
mixture was poured into a flask containing crushed ice and
concentrated aqueous NH4OH (200 mL). The resulting mixture
was bubbled with oxygen for 14 h. The resulting dark blue
mixture was then filtered. The layers of the filtrate were
separated, and the aqueous layer was extracted with CH2Cl2.
The combined organic layer was dried (Na2SO4), concentrated,
and chromatographed [silica, hexanes/ethyl acetate (19:1)] to
afford a colorless liquid (3.17 g, 89%): IR (CH2Cl2) 2230 cm-1
;
1H NMR (300 MHz) δ 2.40-2.54 (m, 6H), 4.94-5.12 (m, 6H),
(24) Hanack, M.; Haisch, P.; Lehmann, H.; Subramanian, L. R.
Synthesis 1993, 387-390.
J. Org. Chem, Vol. 70, No. 20, 2005 7977