Elsevier

Journal of Luminescence

Volume 226, October 2020, 117478
Journal of Luminescence

Perylene derivative films: Emission from higher singlet excited state

https://doi.org/10.1016/j.jlumin.2020.117478Get rights and content

Highlights

  • BuPTCD and PhPTCD present a S2→S0 emission band, named anti-Kasha's fluorescence.

  • The relative intensity (RI) IS1S0/IS2S0 is the same for BuPTCD and PhPTCD solutions.

  • In PVD film, BuPTCD and PhPTCD present distinct RI values between S1→S0 and S2→S0.

  • RI was equally decreased for BuPTCD and PhPTCD PVD films after thermal treatment.

  • Thermal treatment privileges J- and mixed-aggregates of BuPTCD and PhPTCD PVD films.

Abstract

Transitions from the singlet electronic excited states higher than S1 level (S2) to the fundamental state (S0) are unlikely, although such transitions are observed for perylene derivative compounds. This rareness led us to investigate the role of the molecular structure of two perylene derivatives (bis(butylimido) – BuPTCD and bis(phenetylimido) – PhPTCD), as well as their supramolecular arrangements, such as molecular organization, crystallinity, and molecular aggregates (before and after thermal treatment) on the radiative transition S2→S0. The emission spectra of BuPTCD and PhPTCD solutions (monomers) indicated that differences in their molecular structures (lateral groups) do not influence such transitions. Besides, it was verified that the relative intensity (RI) S1→S0 over S2→S0 (RI = IS1→S0/IS2→S0) obtained for BuPTCD and PhPTCD PVD films increases around 15 and 1.5, respectively (in comparison to their respective solutions). However, it was surprising to observe a decrease of RI = IS1→S0/IS2→S0 by a factor of 88 for both BuPTCD and PhPTCD PVD films after their thermal treatment at 200 °C for 2 h. The latter led to an increase of the emission intensity from S2→S0 transition in relation to S1→S0. The decrease of H aggregates, presence of J aggregates and formation of other types of molecular aggregates, induced by thermal treatment, seem to be the cause of the S2→S0 emission increase, which is supported by theoretical calculations.

Introduction

According to the rule proposed by M. Kasha, the fluorescence of a polyatomic molecule occurs only from the first singlet electronic excited state (S1) [1]. This rule can be denominated as Kasha's fluorescence (KF) and describes the behavior of many complex molecules [2,3]. However, evidences have shown that the fluorescence can also occur from singlet electronic excited states higher than S1 level, and this process are expressed as anti-Kasha's fluorescence (AKF) [2]. J. B. Birks predicted the AKF process in 1954 and has reviewed this behavior for different hydrocarbons [3]. Complementary, P. A. Geoldof et al. also verified AKF for vapors of aromatic hydrocarbons and, according to the authors, transitions were observed from a higher singlet electronic excited state (S2) to the ground state [4]. These transitions (S2→S0) are relatively hard to be confirmed because the non-radiative transition S2→S1, named internal conversion (IC), is very fast (typically 10−14 – 10−11 s) and highly efficient, which lead to fluorescence from the lowest singlet electronic excited state (S1) [[5], [6], [7]]. According to A. Nakajima et al. [6], the fluorescence emission from S2 is possible for shorter lifetime, with the process happening before IC. Therefore, although the emission of S2 is less intense due to the fast IC [ [[8], [9], [10]], there is a significant group of molecules presenting this type of emission, such as pyrene [11], 3,4-benzpyrene [4,12], 1,2-benzanthracene [12], 1,12-benzperylene [13] and perylene [6], which is the focus of our study.

Perylene derivatives are polycyclic aromatic organic molecules that have received considerable attention due to their properties and multiple applications, such as the use of perylene derivatives thin films for the development of optic and electronic devices [14]. An important feature of perylene derivative thin films is their supramolecular arrangement, which is directly related to the molecular structure, leading to modifications of the thin film optical and electrical properties [[14], [15], [16], [17]]. In addition, one may take into account the thermal stability of the supramolecular arrangement of the thin film, since changes in the molecular organization after thermal treatment has been reported [[18], [19], [20]]. The latter may be a change in the preferential orientation of a molecule in the film [18], leading them either to disorder [20] or reach a new preferential organization [19].

The correlation between thermal treatment and supramolecular arrangement was studied for bis(butylimido) (BuPTCD) and bis(phenetylimido) (PhPTCD) perylenes by vacuum thermal evaporation (PVD, physical vapor deposition) [21,22]. The aim of this study is to explore possible changes on optical properties (internal conversion) of both perylene derivatives forming PVD films after heating them up to 200 °C for 2 h and cooling down to room temperature. BuPTCD and PhPTCD have the same chromophore as the main molecular structure, however, BuPTCD has two alkyl side chains with four carbons each one in its structure, while PhPTCD has two alkyl side chains with two carbons linked with a benzene ring (insets in Fig. 1). Despite the difference between the chemical structures of BuPTCD and PhPTCD, their optical properties (absorption and emission) are similar when both are in the monomeric form [14]. However, such difference in their molecular structure was responsible for the growth of PVD films with distinct supramolecular arrangements (molecular organization, crystallinity, and molecular aggregation) [14], which lead to changes of the photoluminescent properties of both BuPTCD and PhPTCD PVD films.

Section snippets

Experimental

The compounds BuPTCD (MW 502.56 g/mol) [23] and PhPTCD [24] (MW 602.15 g/mol) were synthetized by Dr. J. Duff, from Xerox Resource Center, Canada, and provided to us by Prof. Ricardo Aroca, from University of Windsor, Canada. Dr. Jim Duff has been performed the synthesis and purification (>99.9%) of a series of perylene derivatives [25,26], including BuPTCD and PhPTCD, which have been applied in experiments using the surface-enhanced Raman scattering (SERS) technique toward single molecule

Photoluminescence spectra of BuPTCD and PhPTCD in solution

The UV–Vis absorption spectra in Fig. 1 were acquired from solutions of BuPTCD and PhPTCD in dichloremethane:TFA (90:10 v/v), at 10−6 mol/L. It is observed two bands, which are attributed to the electronic transition S0→S1 (visible region, with maxima at 623, 486, 456 and 427 nm) [42], as well as bands corresponding to the transition S0→Sn (ultraviolet region, with maxima at 261 and 240 nm), where Sn could be attributed to the higher excited state [42].

From the excitation at 261 nm, it was

Concluding remarks

Photoluminescence spectra of BuPTCD and PhPTCD solubilized in dichloremethane:TFA (90:10 v/v) have shown that both perylene derivatives present an emission band that may be attributed to the radiative decay S2→S0. The emission relative intensity (RI) between S1→S0 and S2→S0 is around 20 for both BuPTCD and PhPTCD solutions, suggesting their distinct lateral groups linked to the chromophore do not affect the internal conversion process. On the other hand, the relative intensity (RI = IS1→S0/IS2→S

CRediT authorship contribution statement

José Diego Fernandes: Conceptualization, Data curation, Formal analysis, Methodology, Writing - original draft, Writing - review & editing. Wallance Moreira Pazin: Conceptualization, Formal analysis, Methodology, Writing - original draft, Writing - review & editing. Wagner Costa Macedo: Conceptualization, Data curation, Formal analysis. Silvio Rainho Teixeira: Data curation, Resources. Sergio Antonio Marques Lima: Conceptualization, Formal analysis, Resources, Writing - original draft. Augusto

Declaration of competing interest

The authors declare no competing financial interests.

Acknowledgments

CAPES, CNPq (grants 448310/2014–7 and 420449/2018–3), INEO and FAPESP (processes 2013/14262–7 and 2016/09633–4) for the financial support. Dr. Ricardo Flavio Aroca, Professor Emeritus, University of Windsor, Canada, for fruitful discussions. This research was also supported by resources supplied by the Center for Scientific Computing (NCC/Grid-UNESP) of the São Paulo State University (UNESP).

References (67)

  • M. Kasha

    Characterization of electronic transitions in complex molecules

    Discuss. Faraday Soc.

    (1950)
  • J.B. Birks et al.

    Stokes and anti‐Stokes fluorescence of 1,12‐benzoperylene in solution

    J. Chem. Phys.

    (1977)
  • J.B. Birks

    Energy transfer in organic phosphors

    Phys. Rev.

    (1954)
  • A.P. Demchenko et al.

    Breaking the Kasha rule for more efficient photochemistry

    Chem. Rev.

    (2017)
  • A. Nakajima

    Fluorescence emission in the gas phase of several aromatic hydrocarbons

    Bull. Chem. Soc. Jpn.

    (1972)
  • J.C. del Valle et al.

    Kasha's rule: a reappraisal

    Phys. Chem. Chem. Phys.

    (2019)
  • G. Quinkert

    Molecular photochemistry. Von N. J. Turro. W. A. Benjamin, inc., New York-amsterdam 1965. 1. Aufl., XIII, 286 S., zahlr. Abb., geb. DM 55.–

    Angew. Chem.

    (1967)
  • D.M. Hercules

    Some aspects OF fluorescence and phosphorescence analysis

    Anal. Chem.

    (1966)
  • W. Herre

    Ralph S. Becker: Theory and Interpretation of Fluorescence and Phosphorescence. Interscience Publishers, John Wiley & Sons, London, New York, Sydney 1969.283 Seiten. Preis: 140 s

    Berichte Der Bunsengesellschaft Für Phys. Chemie

    (1970)
  • A. Nakajima et al.

    Fluorescence spectrum of pyrene vapor: emission from the second excited singlet state

    Bull. Chem. Soc. Jpn.

    (1970)
  • W.R. Dawson et al.

    Radiationless deactivation and anomalous fluorescence of singlet 1,12-benzoperylene

    J. Phys. Chem.

    (1969)
  • P. Alessio et al.

    Supramolecular organization-electrical properties relation in nanometric organic films

    J. Phys. Chem. C

    (2015)
  • D. Yokoyama

    Molecular orientation in small-molecule organic light-emitting diodes

    J. Mater. Chem.

    (2011)
  • E. Moulin et al.

    Advances in supramolecular electronics - from randomly self-assembled nanostructures to addressable self-organized interconnects

    Adv. Mater.

    (2013)
  • T. Del Caño et al.

    Molecular spectra and molecular organization in thin solid films of bis(neopentylimido) perylene

    Appl. Spectrosc.

    (2002)
  • A. Kam et al.

    Evolution of the molecular organization in bis( n -propylimido)perylene films under thermal annealing

    Chem. Mater.

    (1998)
  • S. Rodríguez-llorente et al.

    Spectroscopic characterization of thin solid films of a bis(chlorobenzylimidoperyleneimido)octane derivative

    J. Mater. Chem.

    (1998)
  • J.D. Fernandes et al.

    Physical vapor deposited films of a perylene derivative: supramolecular arrangement and thermal stability

    Mater. Res.

    (2017)
  • J.D. Fernandes et al.

    Supramolecular architecture and electrical properties of a perylene derivative in physical vapor deposited films

    Mater. Res.

    (2015)
  • P.A. Antunes et al.

    Langmuir and Langmuir−Blodgett films of perylene tetracarboxylic derivatives with varying alkyl chain length: film packing and surface-enhanced fluorescence studies

    Langmuir

    (2001)
  • R.F. Aroca et al.

    Surface-enhanced Raman scattering and imaging of Langmuir—blodgett monolayers of bis(phenethylimido)perylene on silver island films

    Appl. Spectrosc.

    (2000)
  • J.M. Duff et al.

    Spectral response and xerographic electrical characteristics of some perylene bisimide pigments

  • E. Johnson et al.

    Spectroscopic properties and packing of Langmuir-blodgett monolayers of perylenetetracarboxylic anhydrides

    Langmuir

    (1995)
  • Cited by (0)

    View full text