T.V. Y et al. / Journal of Molecular Structure 1129 (2017) 248e255
249
accepted and simple experimental method [12e14]. Compared to
other methods solvatochromic method [15,16] provides
pressure and water (50 mL) was added. The resultant precipitate
was filtered under suction to yield crude product which was
recrystallized using ethanol to yield pure product.
a
dependable way to calculated the dipole moment based on the
absorption and emission maxima in different solvents, to that of
conventional methods such as electric dichroism [17], micro-wave
conductivity [18], and thermochromic shift method [19] as they are
limited to simple, small molecules and are considered to be sen-
sitive to equipment. In our previous works, we studied the dipole
moments of various molecules [20e24] using solvatochromic shift
method. We noticed a large alteration in dipole moment of these
molecules in the excited state related to the ground state.
Newly synthesized fluorophores photophysical behavior has to
be thoroughly investigated in order to extricate the information
about the molecules. In this paper we have discussed the synthesis
of (E)-4-((4-(heptyloxy)phenyl)diazenyl)benzyl (((9H-fluoren-9-yl)
Orange solid; yield: 84.2% (1.02 g); mp: 90.6e91.3 ꢀC; 1H NMR
(400 MHz, CDCl3)
d
8.16 (d, J ¼ 8.5 Hz, 2H, HAr), 7.91 (dd, J ¼ 15.9,
8.7 Hz, 4H, HAr), 7.03e6.98 (m, 2H, HAr), 4.40 (q, J ¼ 7.1 Hz, 2H,
OeCH2 Ester), 4.04 (t, J ¼ 6.6 Hz, 2H, OeCH2 Alkoxy), 1.85e1.78 (m, 2H,
O-
b
-CH2 Alkoxy), 1.48 (dd, J ¼ 14.6, 7.3 Hz, 2H, CH2 Alkoxy), 1.42 (t,
J ¼ 7.1 Hz, 3H, Me Ester), 1.37e1.28 (m, 6H, CH2 Alkoxy), 0.88 (t,
J ¼ 6.8 Hz, 3H, MeAlkoxy); 13C NMR (100 MHz, CDCl3)
d 166.2 (C]O),
162.3, 155.3, 146.8, 131.5, 130.5, 125.2, 122.3, 114.8, 68.4 (OeCH2
Ester), 61.2 (OeCH2 Alkoxy), 31.8, 29.2, 29.1, 25.9, 22.6, 14.4 (CH3 Ester),
14.1 (CH3 Alkoxy); FT-IR (KBr, y
, cmꢁ1) 2916, 2847, 1713, 1504, 1466,
1295, 841; Anal. Calc. for C22H28N2O3: C, 71.71; H, 7.66; N, 7.60;
Found: C, 72.06; H, 7.78; N, 7.48%.
methoxy)carbonyl)- -alaninate (Fmoc-al-az) and approximated
D
dipole moments in ground and excited states. Literature survey
revealed that there are no reports available on the photophysical
studies and determination of ground state and excited state values
of the investigated molecule.
2.5. Synthesis of (E)-(4-((4-(heptyloxy)phenyl)diazenyl)phenyl)
methanol (5)
To a solution of LAH (0.154 mg, 4.07 mmol), in dry THF (20 mL)
at 0 ꢀC, 4 (0.500 mg, 1.35 mmol) was added. The reaction mixture
was stirred at room temperature for 2 h. The completion of the
reaction was monitored by TLC. After the completion of the reac-
tion, the reaction was cooled to 0 ꢀC and quenched with 1 N NaOH
solution (30 mL). Subsequently ethyl acetate (20 mL) was added
and the reaction was filtered through celite and extracted using
ethyl acetate (20 mL x 2). The organic layer was dried over sodium
sulfate and concentrated under reduced pressure to give crude
product which was recrystallized using ethanol to give pure
product 5.
2. Experimental
2.1. Materials
All chemicals were obtained from Sigma-Aldich, Alfa Aesar, and
Spectrochem India Pvt. Ltd and utilized without further cleaning.
Every one of the solvents utilized were HPLC evaluation or AR
(obtained from Alfa Aesar). Ethyl 4-aminobenzoate (1) and Phenol
(2) were purchased from commercial source, compound 3 was
synthesized according to reported protocol [25] and was charac-
terized using 1H NMR and 13C NMR. (For the spectral data please
see the supporting information).
Orange solid; Yield ¼ 83.9% (0.371 g); mp: 115.7e116.5 ꢀC; 1H
NMR (400 MHz, CDCl3)
d
7.88 (dd, J ¼ 14.5, 8.6 Hz, 4H, HAr), 7.48 (d,
J ¼ 8.3 Hz, 2H, HAr), 6.99 (d, J ¼ 9.0 Hz, 2H, HAr), 4.76 (s, 2H, OeCH2
Alcohol), 4.03 (t, J ¼ 6.6 Hz, 2H, OeCH2 Alkoxy), 1.85e1.78 (m, 2H, O-
b-
2.2. Measurements
CH2 Alkoxy), 1.53e1.42 (m, 2H, CH2 Alkoxy), 1.37e1.28 (m, 6H, CH2
Alkoxy), 0.89 (t, J ¼ 6.8 Hz, 3H, Me Alkoxy); 13C NMR (100 MHz, CDCl3)
Nuclear magnetic resonance spectra were recorded on Bruker
400 spectrometer. The 1H NMR and 13C NMR spectra experiments
d 161.8, 152.3, 146.8, 143.1, 127.5, 124.8, 122.8, 114.7, 68.4 (OeCH2
Alcohol), 64.9 (OeCH2 Alkoxy), 31.8, 29.4, 29.3, 26.0, 22.7, 14.1 (CH3
were reported in
d
units, parts per million (ppm), and were
Alkoxy); FT-IR (KBr,
y
, cmꢁ1) 3055, 2924, 2854, 1713, 1597, 1466, 1281,
measured relative to residual chloroform 7.26 ppm and 77.0 ppm
respectively in the deuterated CDCl3. All coupling constants J were
reported in Hz. The abbreviations, s ¼ singlet, d ¼ doublet,
t ¼ triplet, dd ¼ doublet of doublet, m ¼ multiplet and br s ¼ broad
singlet were used to describe peak splitting patterns. Reactions
were monitored by using thin layer chromatography (TLC) on
0.2 mm silica gel F254 plates (Merck). Absorption, fluorescence
were analyzed using the spectrophotometer [12]. Density of the
probe was estimated by ACD/Chemsketch software.
1250, 1142, 841. Anal. Calc. for C20H26N2O2; C, 73.59; H, 8.03; N,
8.58; Found; C, 73.76; H, 8.21; N, 8.86.
2.6. Synthesis of (E)-4-((4-(heptyloxy)phenyl)diazenyl)benzy(((9H-
fluoren-9-yl)methoxy)carbonyl)-D-alaninate (7)
To a stirred solution of Fmoc-alanine (6) (228 mg, 0.75 mmol) in
DCM (20 mL), DMAP (7.47 mg, 0.06 mmol) was added at 0 ꢀC and
subsequently EDC.HCl (175.98 mg, 0.918 mmol) and HOBt
(93.72 mg, 0.612 mmol) was added. The reaction mixture was
stirred for 15 min at 0 ꢀC, after which, 5 (200 mg, 0.612 mmol) was
added and the reaction was stirred at room temperature for 6e8 h.
The completion of the reaction was monitored by TLC. After the
completion of the reaction, the reaction mixture was diluted with
water and extracted. Organic layer was separated and dried over
anhydrous sodium sulfate and evaporated under reduced pressure
to give crude product which was recrystallized using ethanol to
yield pure product 7.
2.3. Synthesis of amino acid appended azobenzene derivative
Synthesis of the desired molecule was achieved as shown in
Scheme 1.
2.4. Synthesis of ethyl (E)-4-((4-(heptyloxy)phenyl)diazenyl)
benzoate (4)
To a stirred solution of 3 (1 g, 3.5 mmol) in acetone, K2CO3 (1.2 g,
8.7 mmol) was added at 0 ꢀC and the reaction mixture was stirred
for 15 min. After 15 min. 1-bromo heptane (0.75 g, 4.2 mmol) was
added and the reaction was refluxed for 16 h. The completion of the
reaction was monitored by TLC. After the completion of the reac-
tion, the reaction mixture was concentrated under reduced
Orange solid; yield: 78.8% (0.299 g); mp: 121.5e121.9; 1H NMR
(400 MHz, CDCl3)
d
7.91 (dd, J ¼ 19.3, 8.4 Hz, 4H, HAr), 7.79 (d,
J ¼ 7.4 Hz, 2H, HAr), 7.62 (d, J ¼ 6.6 Hz, 2H, HAr), 7.49 (d, J ¼ 7.9 Hz,
2H, HAr), 7.42 (t, J ¼ 7.3 Hz, 2H, HAr), 7.33 (t, J ¼ 7.1 Hz, 2H, HAr), 7.03
(d, J ¼ 8.9 Hz, 2H, HAr), 5.38 (d, J ¼ 7.4 Hz,1H, NH), 5.34e5.16 (m, 2H,
OeCH2), 4.55e4.36 (m, 3H, eCHAlanine & OeCH2), 4.25 (t, J ¼ 6.4 Hz,