Synthesis and photoluminescent properties of geometrically hindered cis-tris(diphenylaminofluorene) as precursors to light-emitting devices.

Nam-Goo Kang,Long Chiang,Taizoon Canteenwala,Ken Kokubo,Seaho Jeon,Min Wang,Loon-Seng Tan,Chang-Lyoul Lee

doi:10.3390/molecules20034635

Abstract

A novel highly luminescent tris-fluorenyl ring-interconnected chromophore tris(DPAF-C9) was synthesized using a C3 symmetrical triaminobenzene core as the synthon. This structure bears three light-harvesting 2-diphenylamino-9,9-dialkylfluorenyl (DPAF) ring moieties with each attached by two branched 3',5',5'-trimethylhexyl (C9) arms. A major stereoisomer was chromatographically isolated and characterized to possess a 3D structural configuration of cis-conformer in a cup-form. Molecular calculation at B3LYP/6-31G* level revealed the unexpected stability of this cis-cup-conformer of tris(DPAF-C9) better than that of the stereoisomer in a propeller-form and the trans-conformer. The structural geometry is proposed to be capable of minimizing the aggregation related self-quenching effect in the condensed phase. Fluorescence emission wavelength of tris(DPAF-C9) was found to be in a close range to that of PVK that led to its potential uses as the secondary blue hole-transporting material for enhancing the device property toward the modulation of PLED performance.

Highlights

Organic donor fluorophores having extended polarizable ring-branching conjugations in their structure often exhibit good efficiency in photoluminescence that makes them suitable as active components in a number of materials applications, such as optoelectronic devices [1], light-emitting diode (OLED/PLED) cells for flat-panel display [2–4], nonlinear optical (NLO) materials for optical limiting (OL) [5], 3D nano/microfabrication [6], one-photon (1γ) or two-photon (2γ) fluorescence-based optical bio-imaging and labeling substrates for medical diagnosis [7,8], biosensors [9–11], and photo-diagnosis/photodynamic sensitizers for PDT treatments [12,13]
Region were achieved by the attachment of one or multiple 9,9'-dialkyl-2-diphenylaminofluorene moieties on a spherical C60 molecule using a periconjugated keto-bridging unit [30]. It indicated the improvement of light harvesting efficiency by using hindered and branched 3',5',5'-trimethylhexyl (C9) arms to maintain the space-separation of fluorophores intramolecularly within the nanostructure and intermolecularly during possible cluster formation or aggregation in solution
Since tris(DPAF-C9) 7 is highly fluorescence emissive, it can be utilized as a charge-injecting host fluorophore for the study of PLED devices

Summary

Introduction

Organic donor fluorophores having extended polarizable ring-branching conjugations in their structure often exhibit good efficiency in photoluminescence that makes them suitable as active components in a number of materials applications, such as optoelectronic devices [1], light-emitting diode (OLED/PLED) cells for flat-panel display [2–4], nonlinear optical (NLO) materials for optical limiting (OL) [5], 3D nano/microfabrication [6], one-photon (1γ) or two-photon (2γ) fluorescence-based optical bio-imaging and labeling substrates for medical diagnosis [7,8], biosensors [9–11], and photo-diagnosis/photodynamic sensitizers for PDT treatments [12,13] The former four applications involve thin-film device or coating fabrication processes in a solid form of the material.

Results and Discussion

Experimental

Synthetic Procedures

Conclusions