AD—A074 915 BOSTON UNIV MASS DEPT OF CHEMISTRY FIG 10/3ENERGY STORING ORGANIC PHOTOREACT IONS~~ U)AUG 79 6 JONES NOOO1U—76—C ~ o;le2

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I. REPORT NUMBER 2. GOVT A NO. 3. RECIPIENT S CATALOG NUMB ER

Final Report4. TITLE (ind SubISII.) S. TYPE OF REPORT S PERIOD COVERED

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(~, ~~ergy &oring Organic Photoreactions • Final, 11/1/75 — 2/28/79

C~ 4. PERFORMING ORG. REPORT NUMBER

7. AUTHOR(.) S. CONT~~ACT OM GRANt NUMSER(.)

C /Jones~ ~~~~~~

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S. PERFORMING ORGANIZATION NAM E AND A DDRESS 10. PNoa~~AM ELIMEN 1cr . TASK

Department of Chemistry .2~~Boston University L.~~ /1~j .. fi U~ 17 c7 NR 05 1—574/9—26—75

~~~~ Boston. Massachusetts 02215 -

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Off ice of Naval Research August 1, 1979800 Quincy Street DODAAD Code “ N U M U E R O F P AGES

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t)Final vspt. 1 Nov 75~28 Feb 79,

IS. SUPPLEMENTARY NOTES

EIS. KEY WORDS (C.&Muo .n ,ov.r•. .id. SI n.c... ~~ aid td.nH~~ 37 block .ui. b.,)

CDC...) Photochemical energy storage, valence photoisomerization, photosensitization

solar energy storage

I —i

•$?RACT (Cin(Snuo in n v.,.. old. U ~.c...av aid ld.nl t& 37 blOck mi.b.t)

Results of a study of energy storing organic photoreactions are summarized.Discussion includes criteria for efficient photon energy storage, quantumyield and other quantitative results for a variety of photoisomerization andand photoaddition reactions, the nature of intermediates for these.\photo—reactions, photochemistry of charge—transfer complexes, and prospects forphotochemical storage of solar energy.

~~~ 1413 5 OBSOLETE Unclassified/ I **IIPICAY~OW OF tHIS ~~~si (Olin 5.1. lnl. ,.~I

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OFFICE OF NAVAL RESEARCH

Contract N00014- 76-C-0442

Project No. NR 051-574

FINAL REPORT

by

G. Jones, II

Department of ChemistryBoston University

Boston, Massachusetts 02215 $

August 1, 1979

Reproduction in whole or in part is permitted for any purposeof the United States Government

Approved for public release; distribution unlimi ted .

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I

ENERGY STORING ORGANIC PHUTOREACTIONS

INTRODUCTION

The present research program began November 1, 1975 as an outgrowth of

studies supported by the Defense Advanced Research Projects Agency

(5/1/74 - 10/31/75, monItored by ONR). The present work followed generally

the outline of proposals entitled “Storage of Solar Energy Through Valence

Photoisomerization,” (11/1/75 - 1/31/77), “Quinone Cycloadditions: Photo-

chemistry Using Visible Light” (2/1/77 - 1/31/78), and “Photochemistry

Involving Charge Transfer Excited States” (2/1/78 - 2/28/79)

The focus of the research was examination of Isomerization and cyclo-

addition reactions which can be driven by relatively low energy radiation

(near ultraviolet and visible light). Most of the reactions studied were

thermally reversible thus constituting photochemically driven reaction cycles

which potentially store significant quantitttes of photon energy. Potential

appl ications for such reactions include photochemical storage of solar energy

and photochromism suitabl e for optical memory devices. The research

involved in part a study of the photochemistry of visible absorbing charge

transfer complexes. These efforts were expanded to Include preliminary

investigations of the charge transfer excited states of an Important family

of laser dyes, the amino substituted coumarins. 4

ACHIEVEMENTS OF THE PROGRAM(1) Criteria for the successful storage of photon energy as latent heat

through valence photoisomerizatlon have been outlined .1 Energy storing

reactions and potentially useful substrates for photochemical storage have

been identified. Economic constraints on the selection and service life of

photochemical materials to be used in solar energy storage units have been

evaluated.

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2

(2) Several prototype photochemically Induced valence Isomerizatlons

have been evaluated.2’3 Quantum efficiencies , storage enthalpies , and

recycle capability were determined for these systems.

(3) The mechanisms of several energy storing photolsomerizatlons were

studied.3 5 For internal cycloadditlons (the most useful class of energy

storing Isomerizatlons), evidence for the intermediacy of biradicals was

obtained . Partitioning of these intermediates was identif led as the most

important determinant of quantum efficiency for photoisomerizatlon. The

study of cycloadditlon mechanism for a series of linked anthracenes provided

an important evaluation of excimers and biradlcals In the wel l known anthracene

photodimerizatlon reaction.

(4) Cycloaddltion and other reactions of substrates having visible

absorbing chromophores were studled.6 9 An invest igation of biacetyl photo-

addition to alkenes (which leads to small ring oxetane cycloadducts) included

determination of biacetyl phosphorescence quenching constants and quantum

efficiencies, multiplicity , and stereochemistry of addition reactions.7’8

(5) Charge transfer complexes of tetracyanoethylene10 and chloran i l~~with potential alkene photoaddends were characterized. Visible absorption

spectra for these complexes were found to be chiefly influenced by the

electron donor ability of the alkenes. Photoreactions of chloranl)/alkene11

CT complexes were Identified , includ Ing photoadditlon and chloranil photoreduction.

(6) Investigation of courniarin laser dyes’2 Inclu ded the determ ination

of solvent effects on the wavelength and yield of coumarin fluorescence

emi ss ion, and an evaluation of potential quenchers of dye fluorescence and dye

triplets.

( 1) Energy storing organic photoreactions were reviewed wi th emphasis on

photosensitization mechanisms which allow the use of longer wavelength radiation

In driving photo1somerizat1ons.~3 The potential importance of thermal activation

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of low energy longlived excited species (the temperature dependence of quantum

yields of photoreactions which employ low energy photons) was established.

References:

(1) G. Jones, 11 , W.R. Bergmark, and T.E. Reinhard t, Solar Ener_gy, 20, 241

(1978) (TechnIcal Report No. 6).

(2) G. Jones, II and B.R. Ramachandran , J. Org. Chem., 41, 798 (1976)

(Technical Report No. 1).

(3) G. Jones, II , I.E. Reinhard t, and A.M. Halpern , J. Am. Chem. Soc.,

100, 6665 (1978) (Technical Report No. 6).

(4) G. Jones, II and B.R. Ramachandran , J. Photochem ., ~~, 341 (1 976)

(Technical Report No. 3).

(5) W.R. Bermark and G. Jones, II , Nouveau J. de Chimle, 1 , 272 (1977)

(Technical Report No. 5).

(6) G. Jones, II and L.J. Turbini , J. Photochem., 5, 61 (1976). (TechnIcal

Report No. 4)

(7) G. Jones, II and L.J. Turbini , J. Org. Chem ., 41, 2362 (1976) (Technical

Report No. 2).

(8) G. Jones, II , M. Santhanam, and S.-H. ChIang, J. Photochem ., In press

(Technical Report No. 7).

(9) G. Jones, II , M. Santhanam, and S.-H. Chaing , J. Am. Chevn. Soc.,

submitted (Technical Report No. C).

(10) S.A. K,ydd, M.A. Thesis, Boston University , 1977.

(11) G. Jones, II , S. Kanoktanaporn , P.1. Xuan , and J.L. Brunner,

In preparation.

(12) G. Jones, II and S. Kanoktanaporn, unpubl ished results.

(13) G. Jones, II, P.T. Xuan, and S.-H. Chiang , in “Solar Energy: Chemical

Conversion and Storage,” R.R. Hautala, R.B. King, and C. Kuta l , The Humana

Press, Clifton N.J., 1979 (Technical Report No. 9).

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WORK IN PROGRESS - FU I URE DEVELOPMENTS

Studies of energy storing photoisomerization reactions are continuing

wi th support from the Department of Energy. For the photolsomerization of a

derivative of norbornadlene, the limi t of usefu l wavelengths , for an efficient

photoreaction having a large storage entha l py, has been extended past 500 nm.

Studies of the temperature dependent quantum yields of this reaction sensitized

by very low triplet photosensitizers suggest that use of visible light to at

least 600 nm will be possible. Exciplex (electron transfer) mechanisms as

well as energy transfer mechanisms of photosensitization are presently under

Investigation .

Study of coumarin laser dye photochemistry and photophysics continues wi th

the joint sponsorship of the ONR chemistry and physics programs. The objective

of this work is improvement of the efficiency and service life of laser dyes

with the determination of factors influenc i ng dye emission yields and the

identification of dye photodegradation paths and their mechanIsms.

A study of the photochemistry of chioranhl/alkene charge-transfer complexes

has been completed . Submission of a technical report (No. 10) concern Ing this

work is p lanne d .

PUBLICATIONS AND PRESENTATIONS CITING ONR-ARPA SUPPORT

(1) “Catalytic Activit y In the Reversion of an Energy Storing Valence Photo-

isomerization ,” G. Jones, II and B.R. Ramachandran, J. Org. Chem ., ~~~~,

738 (1976).

(2) “The Temperature Dependence of Triplet State Reaction Rate and QuantumYield for an Intramolecular Enone Photocyc loaddition ,” G. Jones , II andB.R. Ramachandran, J. Photochem., ~~, 341 (1976).

(3) “Valence Photolsomerization of l-Ethoxycarbonyl-1H-azePifle: Excited State

Energetics and Multip licity,” G. Jones , II and L.J. Turbini , J. Photochem ..

~~, 61 (1976).

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(4) “Valence Photol somerizatlon of l-Ethoxycarbonyl-lH-azepine and ItsThermal Reversion . Quantitative Aspects Including Energy SurfaceRelationships ,” G. Jones, II and L.J. Turblni , J. Orq. Chem ., 41 ,2362 (1976).

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(5) “Photoisomerization of Linked Anthracenes. A Demanding Test ofMolecular Geometry for In termedi ates in Anth racene Photod imer i zati on ,”W .R. Bergmark and G. Jones, II , Nouveau J. de Chimie ~ 272 (1977).

(6) “The Importance of Intermediate Partitioning in Energy Storing Photo-reactions,” G. Jones, II, 12th Informal Conference on Photochemistry,

- :~ Nati ona l Bureau of Standar ds , Gal thersburg , Maryland , June 28, 1976,

abstract 12.

(7) “Photoisonerlzation of Linked Anthracenes. A Demanding Test of MolecularGeometry for Intermediates in Photodimerizatlon ,” W.R. Bergmark andG. Jones, II , 173rd ACS National Meeting New Orleans , Louisiana , 1977abstract ORGN 108.

(8) “Photon Energy Storage in Orgnaic Materials: The Case of LinkedAnthracenes ,” G. Jones, II, W.R. Bergmark, and T.E. Reinhardt , SolarEnergy, 20, 241 (1978).

(9) “Photoisomerizatlon of Bis(9-anthryl )methane and Other Linked Anthracenes.The Role of Excimers and Biradicals in Photodimerization ,” W .R. Bergmark ,G. Jones , II , I .E . Reinhardt , and A.M. Ha lpern, J. Amer. Chem. Soc.,

• 100, 6665 (1978).

(10) “Exclplex Isonierization - Generality and Potential for PhotochemicalEnergy Storage,” G. Jones , II , Symposium on Nonbiological PhotochemicalConversion and Storage of Solar Energy, 8th Northeast Regional Meetingof the American Chemical Soc i ety, Bos ton, MA , June 25-28, 1978,abstract PHYS 13.

(11) “PhotosensitIzation Mechanisms for Energy Storing Isomerizations.”

G. Jones, II , Symposium on the Chemical Conversion and Storage of SolarEnergy, Southeast Regional Meeting , American Chemical Society, Savanna h,

GA, November 9-11 , 1978, abstract 401.

(12) “The Quenching of Biacetyl Phosphorescence by Alkenes. A Dissection

of Rate Effects on Exciplex Formation and Exciplex Decay for KetoneTriplet Quenching ,” G. Jones, II, M. Santhanam, and S.-H. Chaing ,

J. PPtotochem., submitted .

6

( 13) “Photoadditlon of Blacetyl and Alkenes . Reaction Stereochemistry,,Multiplicity and Photokinetics ,” G. Jones, II , M. Santhanam, and S.-H.Chaing , J. Am. Chem. Soc., submitted .

(14) “Photosensitization Mechanisms for Energy Storing Isomerizations ,”G. Jones, II , P.T. Xuan , and S. -H. Chiang , in “Solar Energy: ChemicalConversion and Storage,” Ed., R.R. Hautala , R.B. Ki ng , and C. Kutal ,The Humana Press, Cl i fton, N.J., 1979

PERSONNEL

Principal Investigator (1974 - 1979) - G. Jones, IIPostdoctoral Research Associates

B.R. Ramachandran (1974-75 , ARPA contract)

L.J. TurbinI (1974-75, ARPA contract), now at Western Electr ic Research

M. Santhanam (1975-77, ONR contract), now Postdoctoral Associate at the

University of Georgia

W.R. Bergmark (1975-76 , supported by ONR contract and National Science

Foundation Science Facul ty Fellowship), on sabbati cal leave from

Ithaca Col lege, now Professor of Chemistry at Ithaca Col lege

S. Kanoktanaporn (1977-78, ONR contract)

H. Divanfard (1977- 78, ONR contract) now assistant Professor of Chemistry

Abbadan University , Iran

uraduato Students

S.A. Kydd, M.A. Boston University , 1977

J.L. Brunner, MA. Boston University , 1977

S.-H. Chiang, Ph.D., Boston University , 1979, now Postdoctoral Associate

at Princeton University

3. Kung

t

7

Undergraduate Students

0. Greenberg, R.A. Boston University, 1978, now at U. of Pennsylvania

Medical School

J. Corwf n, B.A. Boston UnIversIty, 1979. now at School of Medicine .

Boston University

I.E. Relnhardt, now at U. of Massachusetts Medical School

ACKNOWLEDGEMENTS• I and my collaborators are most grateful to the Office of Naval Research

for financial support. Ihis support was part Icularly vital at an

early stage of our work at Boston Un i versity . I wish to thank especially

t Ors. George Neece, Rudy Marcus , and Larry Peebles for their encouragement and

advice

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