Note
DOI: 10.1002/bkcs.10015
BULLETIN OF THE
Y.-K. Song et al.
KOREAN CHEMICAL SOCIETY
Structural and Luminescent Properties of [N-benzyl-N-(2-pyridyl)
methylamine]dichlorozinc(II): Dual Fluorescence of N-benzyl-
N-(2-pyridyl)methylamine
†
‡
†,*
Young-Kwang Song, Sung Kwon Kang, and Young-Inn Kim
†
Department of Chemistry Education and BK21 Plus Team for Advanced Chemical Materials, Pusan National
University, Busan 609-735, Korea. *E-mail: yikim@pusan.ac.kr
‡
Department of Chemistry, Chungnam National University, Daejeon 305-764, Korea
Received June 25, 2014, Accepted September 15, 2014, Published online January 5, 2015
Keywords: Dual fluorescence, Fluorescent Zn(II) complex, Blue emitting material
DualfluorescencewasfirstreportedbyLippertetal.for4-(N,N-
dimethylaminobenzonitrile) (BMABN) in a polar solvent, and
dichloromethane and brine. The crude product was purified
1
by silica gel column chromatography to give bpma as a yellow
1
was explained by the twisted intramolecular charge transfer
oil. Yield 1.94 g (93.2%). H NMR (δ, ppm; DMSO-d , 298
6
2
(
TICT) model proposed by Grabowski et al. According to
K): 8.60 (d, 1H, J = 4.5 Hz), 7.83 (t, 1H, J = 7.8 Hz ), 7.56
(d, 1H, 7.8 Hz), 7.41–7.45 (m, 4H), 7.32 (t, 1H, J = 6.3 Hz),
3.90 (s, 2H), 3.85 (s, 2H), 2.93 (s, 1H).
the TICT model, a molecule with an electron donor and accep-
tor group connected by a single bond may exist as a twisted
structure and exhibit an ICT state upon excitation. Such mole-
cules transform from the exited state to the twisted structure
via aradiationlessprocess, inwhichthe donorgroup isperpen-
diculartotherestofthemolecularframegenerating acomplete
decoupling state. Such molecules generally exhibit dual emis-
sion, which is observed as two well-separated emission bands.
Furthermore, the ratio of the intensities of these two bands is
not dependent on its concentration. This phenomenon is
Synthesis of Zn(bpma)Cl . To a stirred solution of bpma
2
(0.99 g, 5.0 mmol) in methanol (10 mL) was added a solution
of ZnCl (0.66 g, 5.0 mmol) in methanol (10 mL). The reac-
2
tion mixture was then stirred for 8 h at room temperature, fil-
tered, and the white precipitate obtained was collected. White
crystals were obtained by recrystallization from a mixed meth-
1
anol/hexane solution. Yield 1.26 g (75.1%). H NMR (δ,
ppm; DMSO-d , 298 K): 8.66 (d, 1H, J = 5.1 Hz), 8.13
6
3
advantageous in complex biological systems such as cells
(t, 1H, J = 7.8 Hz ), 7.65 (t, 2H, 7.8 Hz), 7.51–7.39 (m, 5H),
or tissues, in which local dye concentrations cannot be easily
controlled, as the ratio of the intensities of these bands can be
applied as a signal in biological systems.
4.91 (s, 1H), 4.00 (s, 2H), 3.91 (s, 1H).
Physical MeasurementsandX-RayCrystallographicAna-
1
lyses. H NMR spectra were recorded in CDCl on a Varian
3
Here, we report the design and preparation ofa novel single-
bond-connected electron donor and acceptor molecule,
N-benzyl-N-(2-pyridyl)methylamine (bpma), which was
anticipated to exhibit dual fluorescence. Based on the TICT
model, we considered that dual fluorescence could be
quenched in metal complexes as metal chelation prevents
the twisting motion between the electron donor and acceptor
groups in the ligand and that metal complexes can be used to
Mercury 300 spectrometer (Varian, Palo Alto, CA, USA).
UV–visible spectra were recorded on a Jasco V-570 spectro-
photometer (Jasco, Tokyo, Japan), and photoluminescence
spectra were obtained using a Hitachi F-4500 fluorescence
spectrophotometer (Hitachi, Tokyo, Japan). Thermal analyses
were carried out on a Mettler Toledo TGA/SDTA 851e ana-
lyzer (Mettler toledo, Greifensee, Switzerland) in a nitrogen
ꢀ
atmosphere at a heating rate of 10 C/min.
4
recognize the metal ions. We synthesized the Zn(II) chloride
X-Ray intensity data were collected at 174 K on a Bruker
SMART APEX-II CCD diffractometer (Bruker, Billerica,
MA, USA) using graphite-monochromated Mo Kα radiation
complex with the prepared bpma ligand, and examined its
structural and luminescent properties with respect to its poten-
tial use as a metal recognition sensor or an active fluorophore.
(λ = 0.71073 Å). The structure of Zn(bpma)Cl was solved
2
using the direct method in SHELXS-97 and refined by full-
2
5
matrix least-squares calculation on F using SHELXL-97.
Experimental
All nonhydrogen atoms were refined anisotropically. The
amine H atom H8 was located in a difference map and
refined freely (N8–H8 = 0.82(2) Å). The other hydrogen
atoms were positioned geometrically and refined using a rid-
Synthesis of bpma. A solution of 2-benzylamine (1.1 g, 10
mmol) in 20 mL methanol was added slowly to a solution of 2-
pyridinecarboxaldehyde (0.95 g 10 mmol) in 20 mL methanol
ing model, with C–H = 0.93–0.97 Å and with U (H) =
iso
and stirred for 2 h. NaBH (0.76 g, 20 mmol) was then added
1.2 U (C).
4
eq
slowly to the solution and stirred for 3 h. The solution was then
evaporated to dryness, and the residue was extracted with
Crystallographic data of Zn(bpma)Cl have been deposited
at the Cambridge Crystallographic Data Center (Deposition
2
Bull. Korean Chem. Soc. 2015, Vol. 36, 374–377
© 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Wiley Online Library
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