Two-Photon Absorption in 3D Chromophores
A R T I C L E S
photodiode array detector. Reaction monitoring and separation were
achieved with a nitro-derivatized silica HPLC column (ES Industries,
catalog # 138213-NO2). The synthesis of 4, 5, 3R, and 3RD have been
reported previously.29
123.698, 122.097, 111.704, 51.261, 31.930, 30.519, 27.469, 22.910,
14.276. EIMS: M+ ) 391.6.
4-Dihexylamino-4′-formyldistyrylbenzene (3). A 100 mL round-
bottom flask was charged with 1.83 g (4.7 mmol) of 2, 2 g (5.6 mmol)
of 1, and a Teflon-coated stir bar and closed with a septum. Anhydrous
DMF (∼25 mL) was transferred to the flask, and the mixture was
stirred. The mixture was cooled to 0 °C, and 168 mg (7 mmol) of NaH
was added through the neck of the flask. The reaction was allowed to
warm to rt and proceed overnight. Workup and the subsequent
deprotection steps were similar to those used for 2 described in detail
above. Additionally, a flash column (90 g silica, 60% CH2Cl2/40%
hexanes) was necessary to isolate the desired compound. The product
was collected as a red solid in 79% yield (1.83 g). 1H NMR (CDCl3):
9.998 (s, 1H), 7.875 (d, 2H), 7.660 (d, 2H), 7.503 (dd, 4H), 7.394 (d,
2H), 7.262 (d, 1H), 7.133 (d, 1H), 7.088 (d, 1H), 6.886 (d, 1H), 6.630
(d, 2H), 3.294 (t, 4H), 1.594 (t, 4H), 1.334 (m, 12H), 0.927 (t, 6H).
13C NMR (CDCl3): 191.833, 148.150, 143.901, 139.015, 135.313,
134.835, 132.263, 130.465, 129.752, 128.121, 127.446, 126.983,
126.490, 124.403, 123.053, 111.764, 51.276, 31.946, 30.519, 27.045,
22.910, 14.276. EIMS: M+ ) 493.7.
4,4,5,5-Tetramethyl-2-(para-methyldiethylphosphonatephenyl)-
1,3-dioxolane (1). Terephthaldehyde mono(diethylacetal) (10 g, 48
mmol) was diluted in ∼35 mL of dry THF in a septum-covered 100
mL round-bottom flask charged with a Teflon-coated stir bar and
maintained under an Ar atmosphere. The mixture was allowed to stir
in a water bath at room temperature. Through the neck of the flask, 2
g (52 mmol) of NaBH4 were added quickly to the mixture and the
flask was resealed. The reaction was allowed to proceed for 3 h.
Approximately 2 mL of water were added with stirring, and the THF
was removed under vacuum. The resulting reaction crude was dissolved
in CH2Cl2 and washed 3 times with deionized water, dried over MgSO4,
and filtered, and the solvent was removed under vacuum for a total of
10.0 g of the resultant benzyl alcohol (essentially quantitative yield).
A portion (6.8 g, 32.3 mmol) of the product was dried in a round-
bottom flask charged with a stir bar and fitted with a needle valve
under vacuum on the Schlenk line overnight and then transferred to a
glovebox. The material was dissolved in ∼35 mL of dry benzene and
stirred at rt. Then 3.5 g (13 mmol) of PBr3 was added and allowed to
react for 1 h. A brownish-white precipitate formed, and the reaction
was quenched with water and diluted in CH2Cl2 and washed 4 times
with brine. The resulting 4-formylbenzylbromide was completely
deprotected (6.3 g, quantitative yield). The product was reprotected
with pinacol in benzene with a trace of tosyl acid in a 250 mL round-
bottom flask fitted with a Dean-Stark trap. The mixture was heated
to 105 °C and allowed to react overnight. A small amount of powdered
NaOH in dry ethanol was added to the cooled reaction mixture and
allowed to stir for 30 min. This solution was filtered over Celite and
washed 3 times with brine. GC/MS revealed complete protection. The
solvent was dried and removed for a total of 9.6 g of product (94%
yield). This material was transferred to a 100 mL round-bottom flask
charged with a stir bar and fitted with a short path distillation head
and receiving flask. Triethyl phosphite (8.0 g, 48 mmol) was added,
and the reaction mixture was purged with argon and then heated to
130 °C overnight. The mixture was cooled, and the excess triethyl
phosphite was removed by vacuum distillation. A total of 11.4 g
Bis(1,4)-(4′′-(4′-dihexylaminostyryl)styryl)benzene (5R). A 25 mL
round-bottom flask was charged with 274 mg (0.7 mmol) of 2, 89 mg
(0.234 mmol) of 5, and a Teflon-coated stir bar and sealed with a
septum. After the flask was flushed with argon, ∼10 mL of dry THF
was transferred to the flask and the mixture was stirred until dissolved.
The flask was cooled to 0 °C, and 78 mg (0.7 mmol) of potassium
tert-butoxide, dissolved in ∼5 mL of dry THF, was transferred to the
reaction mixture. The flask was allowed to warm to rt, and the reaction,
to proceed overnight. The mixture was diluted in CH2Cl2 and washed
3 times with brine. The organic layer was dried over MgSO4 and
filtered, and the solvent was removed under vacuum. The crude was
coated onto silica and was separated on a 90 g flash column with 20%
CH2Cl2/hexanes as eluent, resulting in 152 mg (76% yield) of a bright
1
yellow crystalline solid identified as the product. H NMR (CDCl3):
7.520 (s, 4H), 7.484 (d, 8H), 7.395 (d, 4H), 7.120 (d, 4H), 7.055 (d,
2H), 6.930 (d, 2H), 6.356 (d, 4H), 3.330 (t, 8H), 1.594 (t, 8H), 1.334
(m, 24H), 0.916 (t, 12H). EIMS: M+ ) 853.5
Tetra(4,7,12,15)-(4′′-(4′-dihexylaminostyryl)styryl)[2.2]para-
cyclophane (5RD). A 25 mL round-bottom flask was charged with 712
mg (1.82 mmol) of 2, 226 mg (0.3 mmol) of 4, and a Teflon-coated
stir bar and sealed with a septum. The mixture was flushed with argon,
and ∼10 mL of anhydrous DMF were transferred to the flask. The
solids were dissolved, and the reaction mixture was cooled to 0 °C. A
solution of 251 mg (2.2 mmol) of potassium tert-butoxide in ∼2 mL
of DMF was transferred to the flask, and the reaction mixture was
allowed to warm to rt and react overnight. The mixture was diluted
with CH2Cl2 and washed with deionized water and brine. The organic
layer was dried over MgSO4 and filtered, and the solvent was removed
under vacuum, resulting in a bright orange solid. The solid was triturated
in diethyl ether overnight and filtered off. The recovered solid was
analyzed by HPLC with a nitro-derivatized silica column and found to
contain only cis-trans isomers. The product was taken up in 500 mL
of benzene, the solution was degassed, and the mixture was stirred
overnight while being irradiated with a Hg lamp. The solvent was
stripped, and HPLC analysis revealed a single peak. A total of 302 mg
of bright orange solid was collected for a 60% yield. 1H NMR
(CDCl3): 7.506 (dd, 16H), 7.450 (d, 8H), 7.298 (d, 4H), 7.133 (d, 4H),
7.045 (s, 4H), 6.975 (d, 4H), 6.957 (d, 4H), 6.663 (d, 8H), 3.364 (m,
4H), 3.316 (t, 16H), 2.930 (m, 4H), 1.627 (t, 16H), 1.356 (m, 48H),
0.936 (t, 24H). 13C NMR (CDCl3): 148.051, 138.052, 136.921, 136.193,
129.107, 128.591, 128.083, 127.173, 126.513, 124.722, 123.493,
111.832, 51.314, 33.410, 31.976, 27.523, 27.083, 22.940, 14.307. MS-
MALDI/TOF: M+ ) 1756.0
1
(essentially quantitative yield) of 1 was collected. H NMR (CDCl3):
7.428 (d, 2H), 7.283 (dd, 2H), 5.951 (s, 1H), 3.981 (septet, 4H), 3.140
(d, 2H), 1.287 (d, 12 H), 1.240 (t, 6H). 13C NMR (CDCl3): 129.889,
236.717, 99.868, 82.844, 62.345, 34.404, 33.030, 24.496, 22.364,
16.568. EIMS: M+ ) 356.0.
4-Dihexylamino-4′-formylstilbene (2). A 250 mL round-bottom
flask was charged with 3.47 g (12 mmol) of 4-dihexylaminobenzal-
dehyde, 5 g (14 mmol) of 1, and a Teflon-coated stir bar and closed
with a septum. Next, 60 mL of anhydrous DMF were transferred to
the flask, and the mixture was stirred. The reaction mixture was cooled
to 0 °C and 432 mg (18 mmol) of NaH was added through the neck of
the flask. The reaction was allowed to warm to rt and react overnight.
The crude product was diluted with CH2Cl2 and washed 3 times with
brine. The organic layer was dried over MgSO4 and filtered through a
plug of silica over Celite to remove unreacted 1. The solvent was
removed under vacuum, and the resultant orange oil was diluted with
∼150 mL of THF in a 500 mL flask. Approximately 350 mL of 10%
HCl was added; the reaction flask was heated to 60 °C and stirred
overnight. The THF was then removed under vacuum, and the
remaining aqueous solution was extracted with CH2Cl2 and washed 3
times with deionized water. The organic layer was dried with MgSO4
and filtered, and the solvent was removed under vacuum. An orange
solid was collected and identified as 2 in 88% yield (4.13 g). 1H NMR
(CDCl3): 9.962 (s, 1H), 7.831 (d, 2H), 7.596 (d, 2H), 7.418 (d, 2H),
7.204 (d, 1H), 6.906 (d, 1H), 6.634 (d, 2H), 3.304 (t, 4H), 1.608 (t,
4H), 1.339 (m, 12H), 0.930 (t, 6H). 13C NMR (CDCl3): 191.833.
148.643, 144.971, 134.516, 132.847, 130.473, 128.622, 126.338,
Tetra(4,7,12,15)-(4′′′-(4′′-(4′-dihexylaminostyryl)styryl)styryl)[2.2]-
paracyclophane (7RD). A 25 mL round-bottom flask was charged with
444 mg (0.9 mmol) of 3, 150 mg (0.2 mmol) of 4, and a Teflon-coated
9
J. AM. CHEM. SOC. VOL. 126, NO. 37, 2004 11541