state will enable Zn(PyrPy)2 to be used as a building block for
future miniaturized photonic devices.
In summary, a facile chemical reaction method has been
developed to synthesize Zn(PyrPy)2 micro-octahedra with
regular shape and good crystallinity. Direct fabrication of
size-tunable Zn(PyrPy)2 micro-octahedra is easily achieved
by manipulating the reaction kinetics of metal–organic
coordination. The crystallographic data and structure analysis
for Zn(PyrPy)2 are reported for the first time. XRD experiments
show that the prepared micro-octahedra have good crystal-
linity. We have roughly estimated a very high QY for
micro-octahedra according to the close values of t for
micro-octahedra and solutions. The results presented in this
paper will enable scientists to explore novel applications in the
field of photonic devices.
This work was supported by the National Natural Science
Foundation of China (Nos. 90301010, 20373077, 20873163,
90606004), the Chinese Academy of Sciences (‘‘100 Talents’’
program), and the National Research Fund for Fundamental
Key Project 973 (2006CB806202, 2006CB932101).
Fig. 4 Excitation (dashed line) and emission (solid line) spectra of
Zn(PyrPy)2 in dichloromethane (10ꢄ5 M).
and Weber9b that the Zn(PyrPy)2 has absorbance maxima at
325 and 378 nm, which is consistent with our findings.
Comparing the electronic absorption of free ligand with that
of zinc complex in CH2Cl2 (ESI,w Fig. S12), it is found that the
enhancement of absorption at 366 nm indicates a strong
interaction between the ligand and zinc center.
Notes and references
z Crystal data for Zn(PyrPy)2: C18H14N4Zn, Mr = 351.70, tetragonal,
space group P41212, a = 8.2425(12), b = 8.2425(12), c = 23.659(5) A,
V = 1607.3(5) A3, T = 173(2) K, Z = 4, m(l = 0.71073 A) =
1.532 mmꢄ1, Dc = 1.453 g cmꢄ3
.
The zinc complex reveals one emitting band with a
maximum at 468 nm (Fig. 4), which is consistent with emission
from one excited state. The photoluminescence (PL) quantum
yield (QY) was determined using 9,10-diphenylanthracene as a
standard in cyclohexane (F = 1.00 ꢂ 0.05 at an excitation
wavelength of 366 nm).10 The QY of Zn(PyrPy)2 in CH2Cl2 is
0.66 ꢂ 0.03, while the substituted pyridylpyrrole zinc com-
plexes show diminished QYs.11 The origin of the higher QY
for Zn(PyrPy)2 is presumably attributable to absence of steric
bulk of the substituted group which leads to the higher degree
of coplanarity. The crystal structure of Zn(PyrPy)2 shows that
the angle between the ligand rings, as measured by the
N–C–C–N torsion angle, is only 0.791.
For Zn(PyrPy)2 micro-octahedra with a mean size of 75 mm
and of a solution of 1 ꢃ 10ꢄ7 M, non-monoexponential PL
decay is observed (ESI,w Fig. S13). The PL lifetimes are
listed in Table S2 of ESI.w The PL decay for Zn(PyrPy)2
micro-octahedra with a mean size of 75 mm is a little faster
than that of solution, with a fast-decay component of B0.47 ns
and a B4.36 ns component with a relative amplitude of 0.65.
A fast-decay component of B0.88 ns is observed in the PL
decay for Zn(PyrPy)2 solution of 1 ꢃ 10ꢄ7 M, along with a
dominant B4.03 ns component (with a relative amplitude of
0.82). We could roughly estimate the QY of micro-octahedra
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on the basis of Foctahedron = Fsolutiontoctahedron/tsolution. The
close values of t for micro-octahedra and solution suggests a
high QY of micro-octahedra (Foctahedron E 0.57), because the
QY of Zn(PyrPy)2 solution is very high. High QY in the solid
ꢁc
This journal is The Royal Society of Chemistry 2009
Chem. Commun., 2009, 5457–5459 | 5459