Synthesis and Photophysical Characterization of Novel ESIPT Triazinyl-Benzazole Derivatives

Grasel, Fábio S.; Barreto, Fabiano; Jank, Louise; Stefani, Valter

doi:10.5935/0103-5053.20150148

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Articles • J. Braz. Chem. Soc. 26 (12) • Dec 2015 • https://doi.org/10.5935/0103-5053.20150148 copy

Synthesis and Photophysical Characterization of Novel ESIPT Triazinyl-Benzazole Derivatives

Authorship SCIMAGO INSTITUTIONS RANKINGS

In this work, the synthesis, characterization and photophysical study of new derivatives of triazinyl-benzazoles with fluorescence by excited-state intramolecular proton transfer (ESIPT) are presented. It regards the synthesis of cyanuric chloride with different 2-(2’-hydroxyphenyl) benzazoles, two quite attractive groups from the synthetic and technological point of view. These new compounds have several potential applications such as biological markers and new photoluminescent materials. The derivatives were characterized by ¹H and ₁₃C nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), high-resolution mass spectrometry (HRMS), UV-Vis absorption and fluorescence emission. The dyes are fluorescent by an excited-state ESIPT in the blue-orange region, with a large Stokes’ shift.

Keywords:
benzazole; cyanuric chloride; ESIPT; reactive dye; large Stokes’ shift; fluorescence

Dye	Solvent	λ^a a Absorption maximum; / nm	ε^b b molar absorptivity; × 10^-4 / (L mol^-1 cm^-1)	λ_enol / nm	λ_keto / nm	Δλ_STenol / nm	Δλ_STketo / nm	φ^c c fluorescence quantum yields;
3a	solid state	373	−	−	459	−	−	−
	chloroform	357	4.02	−	467	−	110	0.061
	ethyl acetate	357	3.29	382	470	25	113	0.021
	acetonitrile	353	3.11	380	468	27	115	0.010
	methanol	353	3.49	379	463	26	110	0.016
3b	solid state	350	−	−	492	−	−	−
	chloroform	337	1.22	−	507	−	170	0.009
	ethyl acetate	339	1.02	375	512	36	173	0.010
	acetonitrile	337	1.09	373	508	36	171	0.005
	methanol	339	1.00	396	512	57	173	0.006
3c	solid state	398	−	−	509	−	−	−
	chloroform	354	4.69	−	500	−	146	0.043
	ethyl acetate	352	4.94	440	505	88	153	0.009
	acetonitrile	352	4.80	393	503	41	151	0.004
	methanol	352	5.06	397	498	45	146	0.011
3d	solid state	373	−	−	536	−	−	−
	chloroform	354	1.69	−	540	−	186	0.008
	ethyl acetate	355	1.52	393	549	38	194	0.005
	acetonitrile	351	1.54	402	547	51	196	0.003
	methanol	352	1.44	420	543	68	191	0.006

Dye	Solvent	λ^a a Absorption maximum; / nm	ε^b b molar absorptivity; ×10^-4 / (L mol^-1 cm^-1)	λ_enol / nm	λ_keto / nm	Δλ_STenol / nm	Δλ_STketo / nm	φ^c c fluorescence quantum yields;
4a	solid state	378	−	−	461	−	−	−
	chloroform	312	1.21	375	464	63	152	0.030
	ethyl acetate	329	0.56	373	−	44	−	0.226
	acetonitrile	336	0.80	374	446	38	110	0.025
	methanol	352	0.55	379	−	27	−	0.025
4b	solid state	382	−	−	523	−	−	−
	chloroform	346	2.15	−	517	−	171	0.022
	ethyl acetate	351	1.92	391	518	40	167	0.016
	acetonitrile	347	1.93	384	515	37	168	0.011
	methanol	349	1.60	388	513	39	164	0.009
4c	solid state	396	−	−	510	−	−	−
	chloroform	314	1.92	387	500	73	186	0.036
	ethyl acetate	333	1.44	391	506	58	173	0.036
	acetonitrile	332	2.51	389	444	57	112	0.019
	methanol	335	1.62	394	−	59	−	0.033
4d	solid state	388	−	−	557	−	−	−
	chloroform	358	1.48	−	547	−	189	0.009
	ethyl acetate	361	1.39	425	571	64	210	0.009
	acetonitrile	357	1.40	419	560	62	203	0.006
	methanol	358	1.03	425	564	67	206	0.006

Dye	Solvent	λ^a a Absorption maximum; / nm	ε^b b molar absorptivity; × 10^-4 / (L mol^-1 cm^-1)	λ_enol / nm	λ_keto / nm	Δλ_STenol / nm	Δλ_STketo / nm	φ^c c fluorescence quantum yields;
5a	solid state	409	−	−	449	−	−	−
	chloroform	345	9.63	372	460	27	115	0.048
	ethyl acetate	335	13.40	377	469	42	134	0.019
	acetonitrile	334	12.47	377	464	43	130	0.016
	methanol	336	12.27	381	−	45	−	0.019
5b	solid state	374	−	−	521	−	−	−
	chloroform	345	2.37	−	511	−	166	0.022
	ethyl acetate	351	1.98	380	517	29	166	0.017
	acetonitrile	345	2.30	387	525	42	180	0.013
	methanol	347	1.84	387	521	40	174	0.017
5c	solid state	378	−	−	470	−	−	−
	chloroform	349	8.52	390	497	41	148	0.010
	ethyl acetate	354	10.02	393	499	39	145	0.007
	acetonitrile	352	9.56	393	−	41	−	0.009
	methanol	354	9.82	405	−	51	−	0.025
5d	solid state	402	−	−	561	−	−	−
	chloroform	357	3.08	400	554	43	197	0.005
	ethyl acetate	361	2.73	417	558	56	197	0.004
	acetonitrile	357	2.73	411	558	54	201	0.003
	methanol	358	2.51	423	557	65	199	0.004

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[1] *e-mail: fsgrasel@gmail.com, vstefani@iq.ufrgs.br