DOCSLIB.ORG

An Experimental Study on the Formation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
An Experimental Study on the Formation Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 2008 An Experimental Study on the Formation of Polycyclic Aromatic Hydrocarbons during the Pyrolysis and Oxidation of Catechol[ortho- Dihydroxybenzene]-A Model Compound Representative of Structural Units in Coal, Wood, and Biomass Shiju Thomas Louisiana State University and Agricultural and Mechanical College, [email protected] Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Chemical Engineering Commons Recommended Citation Thomas, Shiju, "An Experimental Study on the Formation of Polycyclic Aromatic Hydrocarbons during the Pyrolysis and Oxidation of Catechol[ortho-Dihydroxybenzene]-A Model Compound Representative of Structural Units in Coal, Wood, and Biomass" (2008). LSU Doctoral Dissertations. 2543. https://digitalcommons.lsu.edu/gradschool_dissertations/2543 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. AN EXPERIMENTAL STUDY ON THE FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS DURING THE PYROLYSIS AND OXIDATION OF CATECHOL [ORTHO-DIHYDROXYBENZENE]⎯A MODEL COMPOUND REPRESENTATIVE OF STRUCTURAL UNITS IN COAL, WOOD, AND BIOMASS A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Chemical Engineering By Shiju Thomas B.S., University of Calicut, India, 1998 May, 2008 Dedication To my parents… ii Acknowledgements First and foremost, I would like to thank my graduate advisor, Professor Mary J. Wornat. Without her encouragement, guidance, and scientific inputs, this research would not have been possible. I am most indebted to her for the freedom she has given me in my research. I would also like to thank the remaining members of my committee, Professor K.T. Valsaraj, Professor J.J. Spivey, Professor K. E. Thompson, Professor J.E. Henry, and Professor D.A. Spivak for their time and valuable inputs. I would like to thank the following for reference standards and/or UV spectra of PAH: Dr. Arthur Lafleur and Ms. Elaine Plummer, of Massachusetts Institute of Technology; Professor Lawrence Scott and Dr. Atena Necula, of Boston College; Prof. Maximilian Zander, of Rütgerswerke; Dr. John Fetzer, of FETZPAHS; Dr. Albrecht Seidel, of Biochemisches Institut für Umweltcarcinogene; Dr. Dianne Poster, of the National Institute of Standards and Technology; Professor William Alworth, of Tulane University; and Dr. Mark McLaughlin and Mr. Ted Gauthier, of Louisiana State University. I would also like to gratefully acknowledge Philip Morris USA for support of this research. I would like to mention Professor K.V. Narayanan for his guidance and support during my undergraduate years. My supervisors and colleagues at Unilever Research India, especially, Dr. Vijay Naik, Dr. Suresh Nadakatti, and Dr. Hari Koduvely, are gratefully acknowledged for their scientific inputs, support, and encouragement. I would like to extend my appreciation to the Chemical Engineering Department for giving me an opportunity to be a part of the graduate student community at LSU. I would like to thank the Chemical Engineering faculty and support staff for their help and support. I would also iii like to thank the Graduate School at LSU for the Economic Development Assistantship and for the Coates Travel awards. I would like to extend my gratitude to Dr. Elmer B. Ledesma for getting me started on my research and for his continuous support throughout my research. I thank my colleagues Jorge, Jerome, Michelle, Sean, Jennifer, Joy, Xia, Franz, Nimesh, and Davis, for helpful technical contributions as well as for making work in the lab more enjoyable. I would also like to acknowledge my friends and fellow graduate students both in and out of the department, and the big Indian community of Baton Rouge for making life away from home enjoyable. This research would not have been possible without the prayers and support of my family, near and afar⎯my parents who have been a constant source of inspiration; my wife and best friend Shamly, for her patience and moral support throughout the last few hectic years; my brother and sister for their prayers and support. I would also like to acknowledge my friend Anish Andheria, who has been a great influence on my life. iv Table of Contents Dedication………………………………………………………………………………………… ii Acknowledgements……………………………………………………………………………….iii List of Tables...……………………………………………………………………………………ix List of Figures……………………………………………………………………………..............x Abstract..……………………………………………………………………………………….xviii Chapter I. Introduction…………………………………………………………………………. 1 1.1. Background and Motivation ...............................................................................................1 1.2. Structure of the Dissertation ...............................................................................................9 Chapter II. Experimental Equipment and Procedures............................................................13 2.1. Reactor System .................................................................................................................13 2.1.1. Fuel Vaporizer ....................................................................................................13 2.1.2. Reactor ................................................................................................................14 2.1.3. Product Collection ..............................................................................................15 2.2. Sample Collection Procedure ...........................................................................................16 2.2.1. Condensed-Phase Products .................................................................................16 2.2.2. Gas-Phase Products.............................................................................................17 2.3. Analytical Procedures for the Identification and Quantification of Products...................17 2.3.1. C1-C6 Hydrocarbon Products ..............................................................................18 2.3.2. Light (< 3 rings) Aromatic Products...................................................................19 2.3.3. PAH Products......................................................................................................19 Chapter III. PAH Product Identification ..................................................................................23 3.1. Introduction.......................................................................................................................23 3.2. Experimental Equipment and Procedures.........................................................................28 3.2.1. Reactor System ...................................................................................................28 3.2.2. Product Analysis .................................................................................................28 3.3. Results and Discussion .....................................................................................................30 3.3.1. Identification of C24H14 PAH..............................................................................32 3.3.1.1. Perylene Benzologues...................................................................................34 3.3.1.2. Fluoranthene Benzologues............................................................................36 3.3.1.3. Pyrene Benzologues......................................................................................39 3.3.2. Identification of Methylene-Bridged PAH .........................................................43 3.3.2.1. UV Spectral Matches for Methylene-Bridged PAH .....................................45 3.3.2.2. Effects of Methylene-Bridging on the UV Spectra of PAH .........................47 3.3.2.3. Identification of C25H14 PAH: Methylene-Bridged Naphtho[2,1-a]pyrene..54 3.3.2.4. Identification of C25H14 PAH: Methylene-Bridged Naphtho[2,3-a]pyrene..60 3.3.3. Identification of Large PAH ...............................................................................63 3.3.4. Other PAH ..........................................................................................................70 v 3.3.5. Comparison with Coal Products .........................................................................71 3.4. Summary and Conclusions ...............................................................................................72 Chapter IV. Effects of Oxygen Addition: Yields of the C1-C8 Thermal Decomposition Products……… ............................................................................................................................74 4.1. Introduction.......................................................................................................................74 4.2. Experimental Equipment and Procedures.........................................................................77 4.2.1. Reactor System ...................................................................................................77 4.2.2. Product Analysis .................................................................................................78 4.3. Results and Discussions....................................................................................................80
Load more

Recommended publications
  • New Electron-Deficient Polycyclic Aromatic Dicarboximides by Palladium-Catalyzed C–C Coupling and Core Halogenation–Cyanation
    New Electron-Deficient Polycyclic Aromatic Dicarboximides by Palladium-Catalyzed C–C Coupling and Core Halogenation–Cyanation Dissertation zur Erlangung des naturwissenschaftlichen Doktorgrades der Julius-Maximilians-Universität Würzburg vorgelegt von Sabine Seifert aus Marktredwitz Würzburg 2017 ii Eingereicht bei der Fakultät für Chemie und Pharmazie am: 18.10.2017 Gutachter der schriftlichen Arbeit: 1. Gutachter: Prof. Dr. Frank Würthner 2. Gutachter: Prof. Dr. Anke Krüger Prüfer des öffentlichen Promotionskolloquiums: 1. Prüfer: Prof. Dr. Frank Würthner 2. Prüfer: Prof. Dr. Anke Krüger 3. Prüfer: Prof. Dr. Ingo Fischer Datum des öffentlichen Promotionskolloquiums: 15.12.2017 Doktorurkunde ausgehändigt am: _________________________ iii iv Abbreviations abs absorbance/absorption Ac acetyl Ar aryl ap applied a.u. arbitrary unit (I)CT (intramolecular) charge transfer CV cyclic voltammetry dba dibenzylideneacetone DBN 1,5-diazabicyclo[4.3.0]non-5-ene DBU 1,8-diazabicyclo[5.4.0]undec-7-ene DCM dichloromethane DDQ 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (TD-)DFT (time-dependent) density functional theory DIPEA diisopropylethylamine DMAP 4-dimethylaminopyridine DMF dimethylformamide DMSO dimethyl sulfoxide dppf 1,1'-bis(diphenylphosphino)ferrocene em emission ESI electrospray ionization ex excitation Fc+/Fc ferrocenium/ferrocene redox couple fl fluorescence iPr iso-propyl HOMO highest occupied molecular orbital HPLC high performance liquid chromatography HR high-resolution I intensity L ligand LUMO lowest unoccupied molecular orbital PADI
    [Show full text]
  • Monoradicals and Diradicals of Dibenzofluoreno[3,2-B]Fluorene Isomers: Mechanisms of Electronic Delocalization
    pubs.acs.org/JACS Article Monoradicals and Diradicals of Dibenzofluoreno[3,2‑b]fluorene Isomers: Mechanisms of Electronic Delocalization Hideki Hayashi,○ Joshua E. Barker,○ Abel Cardenaś Valdivia,○ Ryohei Kishi, Samantha N. MacMillan, Carlos J. Gomez-Garć ía, Hidenori Miyauchi, Yosuke Nakamura, Masayoshi Nakano,* Shin-ichiro Kato,* Michael M. Haley,* and Juan Casado* Cite This: J. Am. Chem. Soc. 2020, 142, 20444−20455 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information ABSTRACT: The preparation of a series of dibenzo- and tetrabenzo-fused fluoreno[3,2-b]fluorenes is disclosed, and the diradicaloid properties of these molecules are compared with those of a similar, previously reported series of anthracene-based diradicaloids. Insights on the diradical mode of delocalization tuning by constitutional isomerism of the external naphthalenes has been explored by means of the physical approach (dissection of the electronic properties in terms of electronic repulsion and transfer integral) of diradicals. This study has also been extended to the redox species of the two series of compounds and found that the radical cations have the same stabilization mode by delocalization that the neutral diradicals while the radical anions, contrarily, are stabilized by aromatization of the central core. The synthesis of the fluorenofluorene series and their characterization by electronic absorption and vibrational Raman spectroscopies, X-ray diffraction, SQUID measurements, electrochemistry, in situ UV−vis−NIR absorption spectroelectro- chemistry, and theoretical calculations are presented. This work attempts to unify the properties of different series of diradicaloids in a common argument as well as the properties of the carbocations and carbanions derived from them.
    [Show full text]
  • Recent Progress in Quinoidal Singlet Biradical Molecules
    Received: November 2, 2014 | Accepted: November 21, 2014 | Web Released: November 29, 2014 CL-140997 Highlight Review Recent Progress inQuinoidal Singlet Biradical Molecules Takashi Kubo Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (E-mail: [email protected]) Takashi Kubo was born in Yamaguchi, Japan, in 1968. He graduated from Osaka University in 1991, received M.Sc. in 1993 under the guidance of Professor Ichiro Murata, and received Ph.D. in 1996 under the guidance of Professor Kazuhiro Nakasuji.After working at Mitsubishi Chemical Co., he joined Professor Nakasuji’s group at Department of Chemistry, Graduate School of Science, Osaka University in 2000 as Assistant Professor. In 2006 he served as Associate Professor. Since 2006 he is Professor of Graduate School of Science, Osaka University. He received the Bulletinof the Chemical Society of Japan Award in 2001. His research interests are structural and physical organic chemistry, mainly the syntheses and properties of polycyclic aromatic compounds with open-shell character, and the development of multifunctional materialsusing a cooperative proton- and electron-transfer system. Chem. Lett. 2015, 44, 111–122 | doi:10.1246/cl.140997 © 2015 The Chemical Society of Japan | 111 Abstract Ph Ph Ph Ph Elusive nature inspin state isafeature of singlet biradical Ph Ph Ph Ph molecules and arises from the weak coupling of unpaired 2 l i i li i f i e ectrons. Th shgh ght rev ew ocuses on recent advances n i i i i ’ f l f experimental approaches for elucidating the electronic structure F gure 2.
    [Show full text]
  • Extension to Nanographenes with Zig-Zag Edges
    ARTICLE DOI: 10.1038/s41467-018-07095-z OPEN Dehydrative π-extension to nanographenes with zig-zag edges Dominik Lungerich 1,2, Olena Papaianina1, Mikhail Feofanov 1, Jia Liu3, Mirunalini Devarajulu3, Sergey I. Troyanov4, Sabine Maier 3 & Konstantin Amsharov 1 Zig-zag nanographenes are promising candidates for the applications in organic electronics due to the electronic properties induced by their periphery. However, the synthetic access to 1234567890():,; these compounds remains virtually unexplored. There is a lack in efficient and mild strategies origins in the reduced stability, increased reactivity, and low solubility of these compounds. Herein we report a facile access to pristine zig-zag nanographenes, utilizing an acid-promoted intramolecular reductive cyclization of arylaldehydes, and demonstrate a three-step route to nanographenes constituted of angularly fused tetracenes or pentacenes. The mild conditions are scalable to gram quantities and give insoluble nanostructures in close to quantitative yields. The strategy allows the synthesis of elusive low bandgap nanographenes, with values as low as 1.62 eV. Compared to their linear homologues, the structures have an increased stability in the solid-state, even though computational analyses show distinct diradical character. The structures were confirmed by X–ray diffraction or scanning tunneling microscopy. 1 Department of Chemistry and Pharmacy, Organic Chemistry II, Friedrich-Alexander-University Erlangen-Nuernberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany. 2 Department of Chemistry & Molecular Technology Innovation Presidential Endowed Chair, University of Tokyo, 7-3-1 Hongo, Bunkyo- ku, Tokyo 113-0033, Japan. 3 Department of Physics, Friedrich-Alexander-University Erlangen-Nuernberg, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany. 4 Chemistry Department, Moscow State University, Leninskie Gory, Moscow, Russia 119991.
    [Show full text]
  • Polycyclic Hydrocarbons
    Polycyclic Hydrocarbons Volume 2 To Sir Robert Robinson Polycyclic Hydrocarbons E. CLAR University of Glasgow, Scotland With a chapter on Carcinogenesis by REGINA SCHOENT AL Medical Research Council, Cm"shaltan Surrey, England VOLUME 2 1964 Springer-Verlag Berlin Heidelberg GmbH ACADEMIC PRESS INC. (LONDON) LTD Berkeley Square House Berkeley Square London, W.1 ISBN 978-3-662-01670-1 ISBN 978-3-662-01668-8 (eBook) DOI 10.1007/978-3-662-01668-8 U.S. Edition published by ACADEMIC PRESS INC. 111 Fifth Avenue New York 3, New York Copyright © 1964 By SPRINGER-VERLAG BERLIN HEIDELBERG ORTGINALL Y PUBLTSHED BY ACADEMIC PRESS INC. (LONDO:t'<) LTD IN 1964 AU Rights Reserved No part ofthis book may be reproduced in any form, by photostat, microfilm, or any othcr means, without written permission from the publishers Library of Congress Catalog Card Number: 63-12392 Preface Polycyclic hydrocarbons are of interest in many fields of science: theoretical chemistry, physical chemistry, organic chemistry, dyestuff chemistry and biology. With regards to the latter, I am indebted to Dr. Regina Schoental of the Medical Research Council for the review in this present work of carcinogenesis by polycyclic hydrocarbons. This book is designed to present the facts in a simple and clear order and to derive empirical rules from them, but it does not present a com­ prehensive theory about polycyclic hydrocarbons. An attempt is made instead to extend classical symbolism into modern structural chemistry. Thus extensive use is made of Robinson's aromatic sextet, which is applied in an uncompromising and strict way. This quasi-classical attempt is encouraged further by such completely unexpected dis­ coveries as those of Dewar benzene and of the electronic asymmetry of formally symmetric hydrocarbons.
    [Show full text]
  • 1 Open-Shell Benzenoid Polycyclic Hydrocarbons Soumyajit Das and Jishan Wu
    3 1 Open-Shell Benzenoid Polycyclic Hydrocarbons Soumyajit Das and Jishan Wu 1.1 Introduction Graphene has been found to be an attractive material since its discovery in 2004 and has drawn enormous interest among researchers owing to its intrinsic elec- tronic and magnetic properties. An indefinitely large graphene sheet, if cut along the two edge directions, can generate two distinct, well-defined small graphene nanoribbons (GNRs), which may be classified into “zigzag” edge (1, trans- polyacetylene) and “armchair” edge (2, cis-polyacetylene) structures (Figure 1.1). If graphene is cut in an all-zigzag fashion or in a triangular shape, the smallest unit that would come out is a phenalene unit (3) with one unpaired electron. The larger frameworks when cut in a zigzag shape will indefinitely lead to a series of non-Kekulé (i.e., open-shell) polycyclic hydrocarbons (PHs, 4–6) possessing one or more unpaired electrons, which can be termed as “open-shell graphene fragments” and are very interesting in terms of academic research. The number of unpaired electrons, or radicals, increases with the size of the framework, starting from phenalenyl monoradical to high-spin polyradical systems (3–6, Figure 1.1). If a graphene sheet is cut in an all-armchair fashion, it would lead to “all-benzenoid PHs,” as their structures can be represented as fully aromatic sextet rings (the six-membered rings highlighted in blue background) without additional double bonds (7). Even though the PHs of such category are larger in size with extended conjugation, they generally show high stability due to the stabi- lization through the existence of more number of Clar’s aromatic sextets (8).
    [Show full text]
  • Polycyclichydrocarbonswithano
    DE GRUYTER Physical Sciences Reviews. 2017; 20160109 Soumyajit Das / Jishan Wu Polycyclic Hydrocarbons with an Open-Shell Ground State DOI: 10.1515/psr-2016-0109 1 Introduction π-Conjugated polycyclic hydrocarbons (PHs) can either accommodate π-electrons in the bonding orbitals to form a closed-shell ground state or show open-shell ground state due to the existence of one or more un- paired electrons [1]. Monoradical PH is comprised of an unpaired electron in neutral molecule in the ground state [2]. Existence of two unpaired electrons (radicals) in a molecule can be classified by either diradical or biradical [3]. In the spin-restricted (R) molecular orbital (MO) representation [4], diradical character tends to increase as the highest occupied molecular orbital (HOMO)– lowest unoccupied molecular orbital (LUMO) gap gets reduced, causing a variation in bond nature from the stable bond regime to the bond dissociation regime through increasing the weight of doubly excited configuration from HOMO to LUMO. In a stable bond limit, i.e., closed-shell, no diradical character exists while in the bond dissociation limit, the perfect biradical or a pure open-shell configuration emerges. Any intermediate state is referred toas “diradicaloid” (diradical-like). Diradicals are even-electron molecules that have one bond less than the number permitted by the standard rule of valence and the two electrons occupy two near-degenerate MOs. The spin multiplicity (2S + 1) of mono- radicals is doublet, whereas for diradicals, two spins can orient in parallel or antiparallel fashion, producing triplet biradical or singlet diradical species. Singlet diradical, as a molecular species, has all the electrons paired but a pair of these electrons, being weakly coupled through anti-ferromagnetic interaction, occupies different parts of the space with a small shared region.
    [Show full text]
  • Chemical Graphs-V Enumeration and Proposed Nomenclature of Benzenoid Cat&Condensed Polycyclic Aromatic Hydrocarbons’
    CHEMICAL GRAPHS-V ENUMERATION AND PROPOSED NOMENCLATURE OF BENZENOID CAT&CONDENSED POLYCYCLIC AROMATIC HYDROCARBONS’ A. T. BALABW and F. HARARY’ ittstitute of Atomic Pbyse, Bucharut, Routnania; University of Michigatt. Ann Arbor, U.S.A.; and University College. London (Rcctrwd in he UK I5 July 1967; acceptrdfor publicarion I4 Sep~tmbtr IW7) m--A modif& definition is proposed for curu~oadcnsed ~~ORWC hydrocarbons. A formula is devised for the aumk of isomers of non-branched eorocoodensc4 arctx~ in function of tbc numkr of hexagons. Proposals arc made for P graph-systematic nomenclature of such arena. based on the chrrac- teristic trw of these systems. THE nomenclature of bcnzcnoid condensed polycyclic aromatic hydrocarbon is extremely compkx. In Clar’s two-volume monograph’ the summary extends over 13 + 48 pages, since the German nomenclature system adopted therein is different from the IUPAC,‘ Chemical Abstracts’ or Ring Index’ systems, and it was necessary to depict the formulae of all compounds discussed in order to indicate rapidly and unambiguously which compounds were discussed. This fact illustrates the basic faults of all nomenclature systems adopted so far in the class of bcnznoid polycyclic hydrocarbons. Trivial names (coroncnc, pyrcnc, ovakne, violanthrent, ttthrene, chryscne, picene, circumanthracene, pcrylene. terrykne, anthanthrene, bisanthene, pcropyrene, (iso)violanthrenc, pyranthrene, etc.) along with semisystematic names (acencs, phenes, heliccncs, rykncs) and with different alternative systems for indi- cating by numbers’ or letters- the homology (bcnz~, naphtho, etc.) make the nomenclature extremely confusing, No attempt has apparently been made to devise a formula for counting the various isomeric polycyclic aromatic hydrocarbons In the present paper we indicate a counting series for a part of the polycyclic hydrocarbons, proposing at the same time a simpk nomenclature system.
    [Show full text]
  • Voltage/ 33O Current Source U.S
    US007 18301 OB2 (12) United States Patent (10) Patent No.: US 7,183,010 B2 Jarikov (45) Date of Patent: Feb. 27, 2007 (54) ORGANIC LIGHT-EMITTING DIODE (58) Field of Classification Search ................ 428/690, DEVICES WITH IMPROVED OPERATIONAL 428/917; 313/504,506 STABILITY See application file for complete search history. (75) Inventor: Viktor V. Jarikov, Rochester, NY (US) (56) References Cited (73) Assignee: Eastman Kodak Corporation, U.S. PATENT DOCUMENTS Rochester, NY (US) 5,281,489 A * 1/1994 Mori et al. .... ... 428,690 5,294.870 A * 3/1994 Tang et al. ....... ... 313,504 (*) Notice: Subject to any disclaimer, the term of this 5,405,709 A * 4/1995 Littman et al. ... ... 428,690 patent is extended or adjusted under 35 6,740,429 B2 * 5/2004 Aziz et al. ........ ... 428,690 U.S.C. 154(b) by 58 days. 2004/0021415 A1* 2/2004 Vong et al. ................. 313,509 (21) Appl. No.: 10/634,324 * cited by examiner Primary Examiner Dawn Garrett (22) Filed: Aug. 5, 2003 (74) Attorney, Agent, or Firm—Raymond L. Owens (65) Prior Publication Data (57) ABSTRACT US 2004/0076853 A1 Apr. 22, 2004 An organic light-emitting device includes a Substrate, an Related U.S. Application Data anode and a cathode disposed over the Substrate, and a (63) Continuation-in-part of application No. 10/131,801, luminescent layer disposed between the anode and the filed on Apr. 24, 2002, now abandoned. cathode wherein the luminescent layer includes a host and at least one dopant. The host of the luminescent layer is (51) Int.
    [Show full text]
  • Band-Edge Excitation of Carotenoids Removes S* Revealing Triplet-Pair
    Band-edge Excitation of Carotenoids Removes S* Revealing Triplet-pair Contributions to the S1 Absorption Spectrum. Daniel W. Polak*1, Andrew J. Musser1, George A. Sutherland3, Alexander Auty2, Federico Branchi4, Branislav Dzurnak1, Jack Chidgey3, Giulio Cerullo4, C. Neil Hunter3, Jenny Clark*1 1 Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK 2 Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, United Kingdom 3 Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, U.K 4 IFN-CNR, Dipartimento di Fisica, Politecnicodi Milano, Piazza L. da Vinci 32, I-20133 Milan, Italy *email: [email protected], [email protected] Abstract: The nature of the low-lying electronic states in carotenoids has been debated for decades. We use excitation-dependent transient absorption spectroscopy and comparison with published results on β- carotene to demonstrate that the so-called S* feature in astaxanthin, echinenone and spheroidenone spectra is due to an impurity in the sample. Excitation at the absorption band-edge results in a transient absorption spectrum dominated by the pure S1 photo-induced absorption, with no contribution from impurities (‘S*’). We find that this S1 absorption resembles the triplet excited-state absorption spectrum, shifted by ~200meV. To explain this, we suggest that the individual triplets that make up the dominant - triplet-pair (TT) configuration of 2Ag contribute strongly to the S1 absorption band. Comparison with recent literature on molecular polycrystalline films which undergo singlet fission suggests the shift could be related to the binding energy of the triplet pair state.
    [Show full text]
  • Synthesis of Circumpyrene by Alkyne Benzannulation of Brominated
    This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Communication Cite This: J. Am. Chem. Soc. 2019, 141, 19994−19999 pubs.acs.org/JACS Synthesis of Circumpyrene by Alkyne Benzannulation of Brominated Dibenzo[hi,st]ovalene † ‡ † § † ∥ Qiang Chen, Dieter Schollmeyer, Klaus Müllen,*, , and Akimitsu Narita*, , † Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany ‡ Institut für Organische Chemie, Johannes Gutenberg-Universitaẗ Mainz, Duesbergweg 10-14, 55099 Mainz, Germany § Institute of Physical Chemistry, Johannes Gutenberg-Universitaẗ Mainz, Duesbergweg 10-14, 55128 Mainz, Germany ∥ Organic and Carbon Nanomaterials Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami, Okinawa 904-0495, Japan *S Supporting Information Scheme 1. Structures of Representative Circumarenes ABSTRACT: A transition-metal catalyzed alkyne ben- zannulation allowed an unprecedented synthesis of circumpyrene, starting from 3,11-dibromo-6,14-dimesityl- dibenzo[hi,st]ovalene (DBOV). The circumpyrene was characterized by a combination of NMR, mass spectrom- etry, and single-crystal X-ray diffraction analysis, revealing its multizigzag-edged structure. Two newly introduced CC bonds in circumpyrene strongly perturbed the electronic structures of DBOV, as evidenced by increased optical and electrochemical energy gaps. This is in good 12 agreement with an increased number of Clar’s sextets as et al. Circumpyrene and circumcoronene, as the next members π of the circumarene family, have been targets of theoretical well as a decreased number of -electrons in the 19,24−28 conjugation pathway of circumpyrene, according to studies.
    [Show full text]
  • 1 Near-Exact CASSCF-Level Geometry Optimization With
    Near-Exact CASSCF-Level Geometry Optimization with a Large Active Space using Adaptive Sampling Configuration Interaction Self-Consistent Field Corrected with Second- Order Perturbation Theory (ASCI-SCF-PT2) Jae Woo Park* Department of Chemistry, Chungbuk National University (CBNU), Cheongju 28644, Korea Abstract An accurate description of electron correlation is one of the most challenging problems in quantum chemistry. The exact electron correlation can be obtained by means of full configuration interaction (FCI). A simple strategy for approximating FCI at a reduced computational cost is selected CI (SCI), which diagonalizes the Hamiltonian within only the chosen configuration space. Recovery of the contributions of the remaining configurations is possible with second-order perturbation theory. Here, we apply adaptive sampling configuration interaction (ASCI) combined with molecular orbital optimizations (ASCI-SCF) corrected with second-order perturbation theory (ASCI-SCF-PT2) for geometry optimization by implementing the analytical nuclear gradient algorithm for ASCI-PT2 with the Z-vector (Lagrangian) formalism. We demonstrate that for phenalenyl radicals and anthracene, optimized geometries and the number of unpaired electrons can be obtained at nearly the CASSCF accuracy by incorporating PT2 corrections and extrapolating them. We demonstrate the current algorithm's utility for optimizing the equilibrium geometries and electronic structures of 6-ring-fused polycyclic aromatic hydrocarbons and 4- periacene. * E-mail: [email protected] 1 1. INTRODUCTION In quantum chemistry, appropriate treatment of the correlations between electronic motions (electron correlation) is crucial to obtain accurate energies.1-5 The perfect descriptions of electron correlation can be obtained via full configuration interaction (FCI), which diagonalizes the electronic Hamiltonian within the space of all possible electronic configurations (determinants).
    [Show full text]