[Bis(iminoalkyl)pyridine]cadmium(II) Complexes
FULL PAPER
Ͻ L1 are observed, again in line with the electron-donating
ability of the alkyl group. The CdII centers in complexes
1Ϫ4 play a key role in enhancing the fluorescent emission
of the ligands. The chelation of the ligands to the metal
center also contributes to the enhancement of the fluor-
escent emission by increasing the rigidity of the ligands,
thus reducing the loss of energy by thermal vibrational de-
cay. However, in the solid state at room temperature com-
plexes 1Ϫ4 exhibit a bright, greenish-blue emission band
with maxima at 482, 485, 488, and 486 nm, respectively
(λmax ϭ 471, 475, 480, and 476 nm for L1ϪL4); these values
are red-shifted by about 80 nm (100 nm for L1ϪL4) from
the emission in solution. This dramatic red-shift of the em-
ission energy for complexes 1Ϫ4 and ligands L1ϪL4 from
solution to the solid state is probably caused by intermolec-
2 H, Py-Hm), 7.89 (t, J ϭ 7.8 Hz, 1 H, Py-Hp), 7.42Ϫ6.85 (m, 10
H, Ar-H), 2.42 (s, 6 H, NϭCMe) ppm. IR (KBr): ν˜ ϭ 3059 (w),
2919 (w), 2860 (w), 1638 (vs), 1594 (m), 1574 (m), 1482 (s), 1445
(m), 1417 (w), 1361 (s), 1319 (m), 1294 (w), 1255 (w), 1220 (s), 1173
(m), 1150 (w), 1118 (m), 1091 (m), 1076 (m), 1027 (m), 992 (w),
969 (w), 912 (w), 874 (w), 823 (s), 808 (m), 774 (s), 762 (m), 743
(m), 707 (s), 697 (m), 658 (w), 645 (w), 551 (w), 520 (m), 468 (w),
443 (w) cmϪ1. C21H19N3 (313.4): calcd. C 80.48, H 6.11, N 13.41;
found C 80.28, H 6.00, N 13.32.
Preparation of 2,6-Bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine
(L2): 2,6-Diisopropylaniline (8.7 mL, 46.1 mmol) was added to a
solution of 2,6-diacetylpyridine (2.5 g, 15.3 mmol) in absolute
methanol (50 mL). After the addition of several drops of formic
acid, the reaction mixture was refluxed for 24 h and then allowed
to cool down to room temperature. The crude product precipitated
as yellow powder. Pure L2 was obtained in 86% yield (6.35 g) upon
ular interactions in the solid state that effectively decrease recrystallization from methanol. 1H NMR (300 MHz, CDCl3): δ ϭ
8.60 (d, J ϭ 7.8 Hz, 2 H, Py-Hm), 7.98 (t, J ϭ 7.8 Hz, 1 H, Py-
Hp), 7.21Ϫ7.13 (m, 6 H, Ar-H), 2.78 (sept, J ϭ 6.8 Hz, 4 H,
CHMe2), 2.30 (s, 6 H, NϭCMe), 1.19 (dd, J ϭ 6.8 Hz, 24 H,
CHMe2) ppm. IR (KBr): ν˜ ϭ 3068 (w), 2960 (s), 2925 (w), 2870
(w), 1646 (vs), 1588 (w), 1571 (w), 1455 (m), 1438 (m), 1406 (w),
1383 (w), 1368 (s), 1321 (w), 1301 (w), 1255 (w), 1240 (m), 1195
(m), 1121 (m), 1103 (w), 1079 (w), 1059 (w), 1041 (w), 994 (w), 961
(w), 936 (w), 886 (w), 829 (m), 801 (w), 770 (s), 758 (w), 744 (w),
691 (w), 634 (w), 533 (w), 443 (w) cmϪ1. C33H43N3 (481.7): calcd.
C 82.28, H 9.00, N 8.72; found C 82.50, H 8.91, N 8.65.
the energy gap.
Conclusion
A series of [bis(iminoalkyl)pyridine]cadmium() com-
plexes have been synthesized and characterized. Complexes
1Ϫ4 and ligands L1ϪL4 have fluorescent emission at
368Ϫ409 nm in dichloromethane solution at room tempera-
ture. Complexes 1Ϫ4 and ligand L1ϪL4 have broad fluor-
escent emission bands in the solid state at room tempera-
ture, with λmax ϭ 482, 485, 488, 486 nm for 1Ϫ4, and 471,
475, 480, 476 nm for L1ϪL4, respectively. Their luminescent
properties show that they are a new class of luminescent
metal compounds with potential applications in optoelec-
tronic devices.
Preparation of 2,6-Bis[1-(2,6-dimethylphenylimino)ethyl]pyridine
(L3): 2,6-Dimethylaniline (6.4 mL, 51.7 mmol) was added to a solu-
tion of 2,6-diacetylpyridine (2.81 g, 17.2 mmol) in absolute meth-
anol (50 mL). After the addition of several drops of formic acid,
the reaction mixture was refluxed for 24 h and then allowed to cool
down to room temperature. The crude product precipitated as a
yellow powder. Pure L3 was obtained in 85% yield (5.4 g) upon
recrystallization from methanol. 1H NMR (300 MHz, CDCl3): δ ϭ
8.56 (d, J ϭ 7.8 Hz, 2 H, Py-Hm), 7.95 (t, J ϭ 7.8 Hz, 1 H, Py-
Hp), 7.11Ϫ6.95 (m, 6 H, Ar-H), 2.27 (s, 6 H, NϭCMe), 2.07 (s, 12
Experimental Section
General: All manipulations were carried out under nitrogen using
standard Schlenk and cannula techniques or in a conventional ni-
trogen-filled glove box. Elemental analyses were performed with a
PerkinϪElmer 240c elemental analyzer. IR spectra were obtained
with a Nicolet Impact 410 FTIR spectrometer using KBr pellets.
NMR spectra were recorded with a Varian Mercury 300 MHz spec-
trometer. UV/Vis spectra were obtained with a PerkinϪElmer
Lambda 20 spectrometer. Luminescence spectra were measured
with a PerkinϪElmer LS55 Luminescence spectrometer at room
temperature. Aniline, 2,6-diisopropylaniline, 2,6-dimethylaniline,
and 2-methylaniline were purchased from Aldrich Chemical Co.
and used as received. Solvents were refluxed in the presence of an
appropriate drying agent, and distilled and degassed prior to use.
For methanol, Mg ribbon was used as drying agent, whereas aceto-
nitrile and dichloromethane were dried with calcium hydride. 2,6-
Diacetylpyridine was prepared according to a published pro-
cedure.[18]
˜
H, CMe) ppm. IR (KBr): ν ϭ 3068 (w), 3019 (w), 2970 (w), 2944
(w), 2915 (w), 2851 (w), 2727 (w), 1646 (vs), 1594 (m), 1567 (m),
1468 (s), 1437 (m), 1366 (s), 1324 (w), 1297 (m), 1247 (m), 1203 (s),
1160 (w), 1148 (w), 1126 (s), 1093 (s), 1071 (w), 1029 (w), 991 (w),
972 (w), 920 (w), 886 (w), 875 (w), 826 (s), 817 (s), 804 (w), 777 (s),
762 (vs), 744 (w), 692 (m), 623 (m), 576 (w), 541 (w), 530 (w), 493
(w), 422 (w) cmϪ1. C25H27N3 (369.5): calcd. C 81.26, H 7.37, N
11.37; found C 80.98, H 7.40, N 11.56.
Preparation of 2,6-Bis[1-(2-methylphenylimino)ethyl]pyridine (L4): 2-
Methylaniline (2.2 mL, 20.5 mmol) was added to a solution of 2,6-
diacetylpyridine (1.1 g, 6.7 mmol) in absolute methanol (25 mL).
After the addition of several drops of formic acid, the reaction
mixture was refluxed for 24 h and then allowed to cool down to
room temperature. The crude product precipitated as a yellow pow-
der. Pure L4 was obtained in 85% yield (1.96 g) upon recrystalliza-
tion from methanol. 1H NMR (300 MHz, CDCl3): δ ϭ 8.42 (d,
J ϭ 7.6 Hz, 2 H, Py-Hm), 7.92 (t, J ϭ 7.6 Hz, 1 H, Py-Hp),
7.23Ϫ6.69 (m, 8 H, Ar-H), 2.34 (s, 6 H, NϭCMe), 2.14 (s, 6 H,
CMe) ppm. IR (KBr): ν˜ ϭ 3068 (w), 3019 (w), 2920 (w), 2856 (w),
Preparation of 2,6-Bis[1-(phenylimino)ethyl]pyridine (L1): Aniline
(2.8 mL, 31.0 mmol) was added to a solution of 2,6-diacetylpyri-
dine (1.70 g, 10.4 mmol) in absolute methanol (30 mL). After the 1648 (vs), 1601 (m), 1569 (m), 1480(s), 1450 (m), 1363 (s), 1321
addition of several drops of formic acid, the reaction mixture was
refluxed for 8 h and then allowed to cool down to room tempera-
ture. The crude product precipitated as a yellow powder. Pure L1
(m), 1294 (w), 1255 (w), 1220 (s), 1187 (w), 1155 (w), 1118 (s), 1095
(w), 1073 (m), 1041(m), 964 (w), 933 (w), 880 (w), 851 (w), 817 (s),
780 (s), 740 (s), 727 (s), 651 (w), 642 (w), 567 (w), 533 (w), 446 (m),
was obtained in 88% yield (2.87 g) upon recrystallization from 405 (w) cmϪ1. C23H23N3 (341.5): calcd. C 80.90, H 6.79, N 12.31;
1
methanol. H NMR (300 MHz, CDCl3): δ ϭ 8.36 (d, J ϭ 7.8 Hz,
found C 80.89, H 6.82, N 12.27.
Eur. J. Inorg. Chem. 2004, 4891Ϫ4897
2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4895
Fan, Rui-Qing
