Synthesis and Characterization of 9,9-diethyl-1-phenyl-1,9-dihydrofluoreno[2,3-d]imidazole-ended Fluorophores

Abstract

A series of π-conjugated compounds ending with 9,9-diethyl-1-phenyl-1,9-dihydrofluoreno[2,3-d]imidazole were conveniently synthesized by condensation of the key intermediate 9,9-diethyl-N²-phenyl-9H-fluorene-2,3-diamine with the corresponding symmetric aryl phthalaldehydes under very mild conditions. The structures of these compounds were confirmed by ¹H NMR, ¹³C NMR, and HRMS. Their UV-Vis spectroscopy data, fluorescent spectroscopy data, and further details of the electronic properties from cyclic voltammetry measurements and theoretical calculations were studied. Most compounds possess good fluorescence-emitting ability with quantum yield of fluorescence values in the region of 0.36–0.92 and display emission within 449–513 nm depending on the molecular nature.

[graphic not available: see fulltext]

Keywords

fluorene / imidazole / synthesis / UV absorption / fluorescence

References

[1] Ramkia NK, Venkateshab G, Sathiyan, et al. A Comprehensive Review on the Reasons behind Low Power Conversion Efficiency of Dibenzo Derivatives Based Donors in Bulk Heterojunction Organic Solar Cells[J]. Org. Electron., 2019, 73: 182-204.

[2] Shawkat MA, Ho CL, Wong WY, et al. Intrachain Electron and Energy Transfers in Metal Diynes and Polyynes of Group 10–11 Transition Elements Containing Various Carbazole and Fluorene Hybrids[J]. Macromolecules, 2009, 42: 6 902-6 916.

[3] Vasilopoulou M, Palilis LC, Botsialas A, et al. Flexible Organic Light Emitting Diodes (OLEDs) Based on a Blue Emitting Polyfluorene[J]. Phys. Status. Solidi. A, 2008, 5: 3 658-3 662.

[4] Hussein EM, Guesmi NE, Majid TK, et al. Synthesis and Photophysical Properties of Benzimidazoles Grafted Pyrazole-containing Pyrene or Fluorene Moiety: A Combined Spectroscopic and Computational Study[J]. J. Photoch. Photobio. A, 2021, 419: 113 456.

[5] Zhen CG, Chen ZK, Liu QD, et al. Fluorene-Based Oligomers for Highly Efficient and Stable Organic Blue-Light-Emitting Diodes[J]. Adv. Mater, 2009, 21: 2 425-2 429.

[6] Seidel P, Seichter W, Schwarzer A, et al. Fluorene Derivatives Bearing Two to Seven Phthalimidomethyl Groups: Syntheses, Crystal Structures and Conversion to Amines[J]. Eur J. Org. Chem., 2021, 2021: 2 901-2 914.

[7] Zhu M, Ye T, Li CG, et al. Efficient Solution-Processed Nondoped Deep-Blue Organic Light-Emitting Diodes Based on Fluorene-Bridged Anthracene Derivatives Appended with Charge Transport Moieties[J]. J. Phys. Chem. C, 2011, 115: 17 965-17 972.

[8] Han Y, Bai L, Yin C, et al. Solution-Processed Diarylfluorene Derivatives for Violet-blue Amplified Spontaneous Emission and Electroluminescence[J]. J.Mater Chem. C, 2017, 5: 9 903-9 910.

[9] Thomas KR, Venkateswararao A, Joseph A, et al. Polarity Tuning of Fluorene Derivatives by Chromophores to Achieve Efficient Blue Electroluminescent Materials[J]. Org. Electron., 2019, 64: 266-273.

[10] Sprick RS, Bai Y, Guilbert AA. Photocatalytic Hydrogen Evolution from Water Using Fluorene and Dibenzothiophene Sulfone-Conjugated Microporous and Linear Polymers[J]. Chem. Mater., 2019, 31: 305-313.

[11] Ma G, Zhao H, Wang J, et al. Studies of Fluorine Auxochrome in C9-Fluorenyl Anthracenes on Optoelectronic Property for Blue Electroluminescent Materials[J]. Dyes. Pigm., 2018, 158: 420-427.

[12] Ma H, Li Y, Wu S, et al. Photo- and Electro-luminescent Properties of 2,7-Disubstituted Spiro[fluorene-9,9′-xanthene] Derivatives Containing Imidazole-derived Moieties[J]. New J. Chem., 2021, 45: 19 381-19 390.

[13] Pham HD, Escrig LG, Feron K, et al. Boosting Inverted Perovskite Solar Cell Performance by Using 9,9-Bis(4-diphenylaminophenyl) fluorene Functionalized with Triphenylamine as a Dopant-free Hole Transporting Material[J]. J. Mater. Chem. A, 2019, 7(20): 12 507-12 517.

[14] Liu Y, Lin J, Xie H, et al. Synthesis and Crystal Structure of Highly Strained Cyclofluorene: Green Emitting Fluorophores[J]. Org. Lett., 2016, 18: 172-175.

[15] Sun W, Zhou N, Xiao Y, et al. Novel Carbazolyl-substituted Spiro [acridine-9,9′-fluorene] Derivatives as Deep-blue Emitting Materials for OLED Applications[J]. Dyes Pig., 2018, 154: 30-37.

[16] Tang F, Peng J, Liu R, et al. A Sky-blue Fluorescent Small Molecule for Non-doped OLED Using Solution-processing[J]. RSC. Adv., 2015, 5: 71 419-71 424.

[17] Chen X, Zhuang X, Wang Z, et al. A Multifunctional Bipolar Host Material Based on Phenanthroimidazole for Efficient Green and Red PhOLEDs with Low Turn-on Voltage[J]. Org. Electron., 2019, 69: 85-91.

[18] Thiery S, Heinrich B, Donnio B, et al. Modulation of the Electronic and Mesomorphic Properties of Alkynyl-Spirobifluorene Compounds as a Function of the Substitution Pattern[J]. J. Phys. Chem. C, 2015, 119: 10 564-10 575.

[19] Jang SE, Joo CW, Yook KS, et al. Thermally Stable Fluorescent Blue Organic Light-emitting Diodes Using Spirobifluorene Based Anthracene Host Materials with Different Substitution Position[J]. Synth. Met., 2010, 160: 1 184-1 188.

[20] Wang W, Zhan C, Xiao SQ. Isomeric Fluorene-based Heteroundecenes with Different Side Chains Anchoring Positions for Small Molecule Acceptors[J]. J. Wuhan Univ. Technol., 2022, 1: 136-147.

[21] Wang T, Zhao S, Zhang W, et al. Synthesis, X-ray Crystal Structure, and Optical Properties of Novel 9,9-Diethyl-1,2-diaryl-1,9-dihydrofluoreno[2,3-d]imidazoles[J]. Monatsh. Chem., 2016, 147: 1 991-1 999.

[22] Chen L, Wang X, Zhang C, et al. n-Conjugated Twin Molecules Based on 9,9-Diethyl- 1-phenyl- 1,9-dihydrofluoreno[2,3-d]imidazole Module: Synthesis, Characterization, and Electroluminescence Properties[J]. Monatsh. Chem., 2020, 151: 917-924.

[23] Wang X, Zhang C, Wang T, et al. Synthesis and Application of a Novel 9,9-Diethyl-1,2-diaryl-1,9-dihydrofluoreno[2,3-d]imidazole for Blue Organic Light Emitting Diode[J]. Chin. Chem. Lett., 2020, 31: 64-66.