Design, Synthesis and Electroluminescence of Organic Conjugated Compounds Based on Pyrene-imidazole†

doi:10.7503/cjcu20170049

Abstract

Abstract:

A series of organic fluorescent materials based on pyrene-imidazole was designed and synthesized by one-pot reactions. The compounds were thoroughly characterized by ¹H NMR and ¹³C NMR spectroscopy, mass spectroscopy and elemental analysis and corresponded well with their expected structures. The conjugation degree, spatial structure, the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) energy levels are fine-tuned by the various substituents at C1 position of imidazole. They also increase the thermal stabilities of these pyrene-imidazole derivatives. These materials show potential applications in organic light-emitting diodes.

Key words: Pyrene-imidazole, One-pot reaction, Organic light-emitting diode, Quantum efficiency

CLC Number:

O626

TrendMD:

LIU Yulong, LU Fang, LU Ping. Design, Synthesis and Electroluminescence of Organic Conjugated Compounds Based on Pyrene-imidazole^†[J]. Chem. J. Chinese Universities, 2017, 38(4): 583.

Figures/Tables 9

Scheme 1 Synthetic routes of four pyrene-imidazole based materials

Fig.1 Molecular optimized configurations

Fig.2 Molecular electronic orbital distributions

Fig.3 Cyclic voltammogram curves in CH2Cl2(oxidation) and DMF(reduction) measured with 0.1 mol/L (Bu4N)PF6 as supporting electrolyte at a scan rate of 100 mV/s

Fig.4 Normalized absorption(A, C) and emission spectra(B, D) in tetrahydrofuran (A, B) (10-5 mol/L) and in ﬁlm(30 nm)(C, D)

Table 1 Optical and electrochemical properties of the compounds

Compd.	λ_sol/nm		λ_film/nm		$E gap c$ / eV	$E gap d$ / eV	FWHM^e/ nm	(λ_film- λ_sol)^f/ nm	$Φ fl g$ (sol/film)
Compd.	Abs^a	PL^a			$E gap c$ / eV	$E gap d$ / eV	FWHM^e/ nm	Abs^b	PL^b
PyPI	291, 330, 382	384, 405, 430	297, 338, 385	454	3.20^c	3.24^d	80	70	0.75/0.18
PyCzI	291, 340, 385	392, 414, 438	297, 347, 388	433	3.14^c	3.12^d	64	41	0.66/0.52
Pyd-CzI	293, 340, 385	396, 415, 438	296, 347, 388	442	3.13^c	3.00^d	61	27	0.58/0.48
PyTPAI	293, 350, 387	409, 427	298, 355, 389	451, 464	2.88^c	2.73^d	80	24	0.99/0.65

Table 1 Optical and electrochemical properties of the compounds

Compd.	λ_sol/nm		λ_film/nm		$E gap c$ / eV	$E gap d$ / eV	FWHM^e/ nm	(λ_film- λ_sol)^f/ nm	$Φ fl g$ (sol/film)
Compd.	Abs^a	PL^a			$E gap c$ / eV	$E gap d$ / eV	FWHM^e/ nm	Abs^b	PL^b
PyPI	291, 330, 382	384, 405, 430	297, 338, 385	454	3.20^c	3.24^d	80	70	0.75/0.18
PyCzI	291, 340, 385	392, 414, 438	297, 347, 388	433	3.14^c	3.12^d	64	41	0.66/0.52
Pyd-CzI	293, 340, 385	396, 415, 438	296, 347, 388	442	3.13^c	3.00^d	61	27	0.58/0.48
PyTPAI	293, 350, 387	409, 427	298, 355, 389	451, 464	2.88^c	2.73^d	80	24	0.99/0.65

Fig.5 DSC(A) and TGA(B) curves under nitrogen at a heating rate of 10 ℃/min

Table 2 Electroluminescence properties of the devices

Device	CIE^a(x, y)	Voltage^b/V	CE^c/(cd·A^-1)	PE^d/(lm·W^-1)	L^e/(cd·m^-2)	EQE^f(%)
PyPI	(0.160, 0.244)	4.0	1.95	1.24	9615	1.29
PyTPAI	(0.162, 0.168)	3.5	1.66	1.36	4964	1.16
PyCzI	(0.157, 0.166)	3.0	1.91	1.45	8063	1.62
Pyd-CzI	(0.161, 0.194)	3.5	1.97	1.52	7217	1.61

Fig.6 Energy level diagrams of the investigated organic light-emitting diodes(OLED)(A), current density-voltage(J-V) characteristics(B), current efficiency vs. voltage curves(C) and electroluminescence(EL) spectra measured at 7 V(D)

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