D-R136 330 PHOTOCHEMISTRY AND PHOTOPHYSICS OF LASER DYES(U) BOSTON i/lUNIV MA DEPT OF CHEMISTRY G JONES 31 OCT 83 TR-8N00014-79-C-0054

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REPORT DOCUMENTATION PAGE READR COMISTRFORM1. REOR MUMME - G ACESIN No X REI11I CATALOG HUMMER

Technical Report No. 8 - final ______________

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Photochemistry and Photophysics of Laser Dyes Final, 11/1/78-10/31/82

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G. Jones, II N00014-79-C-0054

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S It. CONTROLLING OFFICE NAME AND ADDRESS IL REPORT DATEOffice of Naval Research October 31, 1983Eastern/Central Regional Office Is. NUNWER oF PAGES666 Suamer Street, Boston MA 02210 10

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16. AIPOLEMEIINTARY NOTUS DE

"I' medium effects on laser dyes, coumarin emission yields

J.LJ Results of a study of photophysical properties and mechanisms of photo-degradation of coumarin dyes are summarized. Discussion includes effectsof polar media on dye emission yield and lifetime, solubilization ofdyes in water with surfactants, products of dye photodegradation, electrontransfer properties of coumarin dyes, mechanisms of dye photodecomposition,K and recommendations of restorative procedures for dye media.-,-L

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PHOTOCHUUY MND PUOTOPHYICS OF LaERDYE

The present research program began November 1, 1973 as an outgrowth of

work In orgaico photochemistry on sensitizing dyes and meohaniass of pho-

tainduced isamerization reactions which was supported earlier by the Office

of Naval Research. The program encompassed the original 12-month contract

(100014-79-C-0054) , two funded renewals, and an extension period which

ended. October 31. 1982 * xperimental work related to the program contin-

ued until June, 193, and manuscript and report preparation extended to

November, 1933.

The objectives of the program involved a thorough investigation of

phortiphysica2, and photochemical properties, of the important "blue-green"

oumarin laser dyes directed to the Improvement of service life end lasing

effioieaoy at dye media. The proposed studies included measurement of the

important pbotophyuical parameters for a variety of dye structures with

emphasis on medius effects on fluorescence quantum. yields and lifetime for

the ooaina and the determination of the yields of dye triplets and their

properties. Other goals Involved the Identification of pbotoproducts copy

obtained on degradation of dyes under steady Illumnination. Mmchbanisms of C

degradation were also to be assigned where possible and recommendations set In Foir

forth concerning minimization at decomposition. E

Other lines of research Included evaluation of dye properties In aque- -,t10

ous media with empsi on the possibilities of solubilization of dyes

%% .U~tjj iy Cod e$

UTA and/oDhmbuama UamDist

pae 2

uaing surfactant additives and the development of media having advantages

of reduced optical inhomogeneity under lazing conditions. The effects of

quenchers of dye excited states were also of interest in tems of estab-

lishl the types of additives which might stabilitae dye media to

iCuu Vm or TH PROGRAM

The progra was suoessful in providing now information and recomen-

dations conerwning each of the objectives outlined above. A brief sumry

is provided here with references to papers which have been published or

recently submitted and the appropriate technical reports to ORR.

3tructures I - I, identify most of the ooumarin dyes which were included in

our investigations.

(1) A study of the quantum yields of fluorescence and singlet life-

times (the latter deteraned by time-oorrelated sinlet-pboton counting)

for structure J, - I established the importnce of a rotatory non-radiative

decay path whith Is Impotant for selected dyes in polar media. The impor-

taft structura feature, the umefubered amine group at the 7-position,

and the evolutim at exited spe"es in term of planar and twisted intra-

maleoular obarg trnser states. and M.1 were identified.1

(2) Use red shifts of absorption and emission bands of oumarin dyes

in solvents of "igh polarity were investigated. The solvatoohromim pro-

vided liner errelatia with well known solvent parameters which reflect

mersal polrity-polarssbUlty and hydrogen bonding properties of organic

media. Sho quite regular dependenoes can be helpful In woolvent tuningm of

page 3

the wavelength at mission (lasing) .2

(3) An investigation of quenching, of ooumarin ainglets and triplets by

electron transfer agents (both donors and acceptors) was carried out.

Dedox potentials determined by cyclic voltimetry, rate constants for bimo-

lecular quenching of excited dye, and transient absorption obtained by

flask photolysis were used to determine that coumafin dyes have a moderate

tendency to interact with either electron donors or acceptors. Then*

observations will be helpful In selecting additives (quenchers) which may

echance stability without leading to unwanted new photoohemistry.'

(4) A previously ureported phenomenon, the concentration (self)

quending of fluoresceae for oaumarias 3 - 4 was observed. A correlation

was f aer =A*de between li eulelar self reaction at excited dye with the

qu um yield i photoea on. The aLnglet eoumarin exoited state was

idmtified as primarily resposuible for potodeoomposmiton which leads to

.elklaties (loes or ame mbsitnt groups - e.g., I + ). The large-

ly inreative triplet state was observed by flash photolyLs and its

uuoueaular and bimoleeular decay rate parmeters determined.'

(S) A more agog eweave egsmitLon of solvent effects on fluores-

mas letims and quantum yield revealed that certain dyes which ar

m-rgid* with resmect to the smine group. I - 11, are relieved of the

qu stem wast a acm-radiative rotatory decay prevalent In polar edia (vide

sup"a) due to mbtle structural features which could be outlined In detail.

Ur thecry regarding rotatory decay of polar ecited states was developed

with eapsasis on the role of local excited state bond orders. ftlaslon

puepertes In low telperature glasses, deuteratod solvents (Including

in. M.

page 4

uster) and triplet state properties for representative dyes were also

(6) The effects of suractants In solubiliaing hydrophobic oounarin

die in water wor establiahed. Cationlo and anionic detergents as vell as

oyclodetrins were effective in producing moderately concentrated aqueous

dye solutions which, In m oas, were strongly missive. Eission pro-

prties# photodegradation. Interaction with quenohers, and flash

pbotoheistry of solubLlized ooumrns were investigated.'

(7) New products o couma-in photodegradation were identified. A path

tur decomposition involi reduction of the coumarin double bond

(S-position) and a pbotoozidation involving the mine moiety for a rigid

dVe () were established. Zntersystem crosming yields (by triplet count-

Ing) were dete mimd and a nohanim for oouaxin photolysis Involving

sinlet dye and the produotion o radicals was proposed.'

V0E 11 PllOGREM MiD FIS WLOMUTSI

Additional experiment& Involving the dependence of ooumarin absorption

and mission an .ediu are currently underway. Those results will lead to

further parmeterization at solvent and emission (lasing) proporties and

will be the subJect of a future publication. Studies are also underway

involving the observation of chemically induced dynamic nuclear polariza-

tion (CIXMP) for dye solutions during photolyals. This investigation,

carried out with the collaboration of Dr. J. iargon of IBM Researoh

Labratarios. San Jon is directed to unambiguous Identification of pro-

posed radioal intermedates which are responsible for photodegradation.

page s

£ series ot experiments is planned around a new dye laser facility at

Bostoa University. As the result of a recent DOD Instrument grant, a

IdTAG Puped dye laser (Quantel Datahrom 5000) has been purchased and

will be used to detwris ihotoatability of dyes under 1-sn conditions.

The facility will allow Investigation at dyes under intense flashlamp illu-

mination ()1SO m/8 m pulse @ 10 f) for product studies and for transient

detection of absorption (LCroy 100 Nlf transient digitizer and CANACILSI

computer Interface). Depending on the availability of funds, the program

will continue with emphasis on the following themes:

(1) Identification at transient Intermediates such am radicals or red-

ioal-ica which Induce dealkylation, net redox reaction. or polymerization

ot laer dyes

(2) the behavior of dyes In Ounusual media: surfactant solutions,

oeleimztrin and other inclusion complexes; protectione of d4ye structure

amd stined emiss o in aereber es media

(S) t0e design and synthesis of laser dye& for the ultraviolet

(00-400 m) with phdais on the faentals of photolysis mechanim and

mm-aiistive dewy (rotatory paths, electron transfer) established In the

oommarin study

(4) the disoovery of mltiple photon photochemical processes for laser

dyes under high intensity fladamp Illumination (lasing conditions)

page 6

PrIdpa Investigator

Guiltord Jois, .1, Professor of Chemistry, Boston University

(]JIn-U)

postdootmal Research Associates

V. I. Jackson (ft. D., U. of California, Santa Crus): December 1,

in8 through Decenber 31, 1900; am at IBM Research Laboratory, 3.

VIadil, 3ev York

V. No Niprk (Ph. D., sNsaohusetts Institute of Technolog,

Professor at Cmastry. Ithaca College): June 15, 19U through

October S1, 1981; returned to Ithaca College after mabbatical year

at Boston University

Graduate Student

S. F. Oriffin (. 8., U. of 3bsachusetts): January - June, 1983;

centImlng In the Ph. D. program at Boston University

LM~

page 7

ndgMuaate Student

C. Chol (B. A., Boston University, 1981): January, 1980 through

August, 1981; presently a graduate student in Ph. D. program, U. of

Chiogo

Seor Collaborator

A. I. %lpen (Associate Professor of Chemistry, Northeastern

Unversity): assisted vith fluoresoence lifetime measurements during

: UEMAL MOM3

1. idwmlal Bopet No. 1. Jamsry 1. 1980

gbi ufeel em onlurmeeee Omantum Yields and Lifetimes f'r Coumarin

1.emm Wm." 0. deMs. UI. V. It. Jealon. and A. 1. Halpern, Ches.

YAM Ios., 72, SK (190).

2. %b~eM luput No. 2. JMiany 1. 1980

Oftlw 3teeU em FttUsal ftameters fo.' Coarin Laser- Dyes,

6. Jm . U., 1. I. fem, S. Kgaaktanaporn. and A. K. Halpern,

O,.,. . 381, (1960).

page8

3. Technical Report No. 3, October 31, 1983

Mlectron Donor-acceptor Quenching and Photoinduced Electron Transfer

far Comarin Dyeos. 0. Jones, TI, 3. F. Griffin, C. Choi, and W. R.

Berark. J. PIys. Cha,, submitted.

4. Technicoal Report No. 4, October 31, 1983

Photodegradation of Coumarin Laser Dyes. An Unexpected Singlet

3elf-quencbing Nehanim,' 0. Jones, 11, and V. R. Berpgark, J.

Photoches., submitted.

S. Technical Report No. S, October 31, 1983S3olvent Effocts on Eission Yield and Lifetime for Coumarin Laser

Dyes. Requirments for a Rotatory Decay Neehanie...o Q. Jones, I1, V.

1. Jackson. C. Cho., and V. 1. Dwpmrk, J. An. Chea. 3oO.. submitted.

S. Technical Report No. 6, October 31, 1913

OPhotophysioal and Photooh ioal Properties of Coumrin Laser Dyes in

hmphoipilic Media,* 0. Jones. II v. . Jackson. . K anktanaporn, and

V. 3. Bergeark. J. An. Chen. oc.. submitted.

7. Teobical Report No. 7. October 31, 198S

*roats of PhotodegradatLon for Coumarin Laser Dyes. 0. Jones, II,

V. t. Jackson, and W. R. Derpmr, 9 tos Coan., submitted.

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