Photochemistry of Naphthonitrile-Olefin Systerns

8/2/2019 Photochemistry of Naphthonitrile-Olefin Systerns

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McMaster University

DigitalCommons@McMaster

Open Access Dissertations and Theses Open Dissertations and Theses

1-1-1978

Photochemistry of Naphthonitrile-Olefin SysternsRoderick Charles Miller

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Recommended CitationMiller, Roderick Charles, "Photochemistry of Naphthonitrile-Olefin Systerns" (1978).Open Access Dissertations and Theses. Paper3853.http://digitalcommons.mcmaster.ca/opendissertations/3853
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DISCUSSIONP A R ~ I: PRODUCT STRUCTURE AS A FUNCTION OF SOLVENT

i. ",-S'ol'vents of Low 'Pol'arity2. S61vents of High ~ b l a r i t y'. l ., PART II: MULTIPlICITY OF ~ H NAPHTHONITRILE EXCITED STATE" ' '' . PART I I I : NATURE OF THE l ~ N A P H T H O N I T R I L E O L E F ! N EXCIPLEXESPART IV: F A ~ T O R S AFFECTING rXCIPlEX FORMATION

1. E f f e c ~ of D o n o r ~ a n d Acceptor Structure on F l u o r e ~ c e n c eQ u ~ n c h i n9' Rate' . . .

2. Effect Of, Sol,vent orf the Fluorescence Quenchi.ng Rate

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.. PART II: PREPARATION OF PHOTOADDUCTS

PART V: EFFECT OF S O L V ~ N T . ON EXCIPLEX DECAYPART VI: SUMMAR

6"PERIMENTALPART I: M A T E R ~ A L S ~ ?OLVENTS, AND INSTRUMENTATION

1. Ma teri a1s2. Solvents .

, .3. Ins trumen ts

1. 'Experiinental Equipment2. Absolute Quantum Yields of product Formation3. Quantum Yi-elds 'as a Function of Ql:Jenche.r Concentr.ation'4: ' . S e n ~ i ' t i z a , t ; o n Ex:oer-inients~ Effeet of:Oi-l-butvlnitroxide on Reaction o f ' l ~ N a p h t h o ~nitrile and . r e t r a m e t h Y } e t y y l ~ n ~ - . ' "6. Vari at ion in' E f f i c i ~ ~ C Y ' ~ f ' F o ~ ; a t i ~ n 6f Cyclobutane 42with Solvent ..-

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131132132132

134136136137

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1. Irradiation of 2-Naphthonit ri le and Tetramethy1ethy1enein Benzene . .2. Irradiation of 2-Naphthonitri1e and'Tetramethy1ethy1enein. 1.2-0imethoxyethane3. Irradiation ~ l-Naphthonitri1e and Tetramethy1ethy1enein l,2-Dimethoxyethane4., Irradiation'of l-N'aphthonitri1e and T e t r a ~ e i h y 1 e t h , l e n e. in Meth.ano15. I r. radiat ion of l-Naphthonitrile and Tetramethy1ethylenein Acetonitrile6: Irradiation of 2-Naphthonitri1e and T e t r a m e t ~ y l e t h Y l e n ~in .2,2;2-Trifluoroethano17. Irradi ation of l-Naphthonitri1e and 1,2-Dimethy1.cyclQpentene in ' B ~ n l e n e .8. I r r a d i a t i o ~ of l-NaphtAonitrile and 1 , 2 ~ D i m e t h y ~ c y c l o -pentene in l , 2 ~ D i m e t h o x y e t h a n e. 'PART I I I : QUANTUM Y'IElO DETERMINATIONS,

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, PART IV: FLUORESCENCE QUENCHING.1. Reduction Potentials2. Solvent Z Value3. Stern-Volmer, Quenchinq Studies4. Exciplex F'luorescence as a Function of quencherConcentra ti on. ' \5. Exciplex Q u e n ~ i n g

PART V: EXCIPLEX E M I ~ S I O N QUANTUM YIELD AS' A FUN(TION OF SOLVENT

159160160162165168

1. Quantum Yield of l - N a p h t n o n i t r i l e - T e t r a ~ e t h y l e t h y l e n e 'Exciplex Emission as a Function of Solvent 168I 2. Quantum Yield of l - N a p h t h o n i t r i l ~ - l ,2-Dimethylcyclopentene

E x c ~ p l e x E m i s ~ i o n as a Function of Solvent 170PART VI: MEASUREMENT OF NANOSECOND LIFETIMES 172REFERENCES

. . . viii

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INTRODUCTION

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rPART I: GENERAL THEORY OF EXC!TED STATESMost molecules in their electronic state of l ~ w e s t energy have all

electron spins paired and are in a singlet state (net spin angular momentumof zero) designed SO' When a molecule absorbs electromagnetic radiationits energy increases by an amount equal to that of the absorbed p h o t o n ~ asgiven by the E i ~ s t e i n relationship

E = h = hC/A = hcvwhere h v ~ c ~ A and v are Planck's constant, the frequency of the radiation,the velocity of 1 i g h ~ ~ the wavelength and the wavenumber of the radiation,

Ir e s p e c t i v ~ l y . The-absorption of visible or ultraviolet radiation promotesan electron from a bonding o r n o n ~ o n d i n g orbital to an,unoccupied antibonding. ,orbital. This process is faster (10- 15 sec) than nuclear movement (Franck-Condon Principle), ~ n spin multiplicity is conserved g i v i n g ~ a n excited singlet

state, SN' The excitation may occur intp anyone of 'the upper vibrationaland rotational energy sublevels in the SN state. In condensed media (liquidor solid ) the molecule rapidly (10- 12 sec) loses this excess vibrationalenergy by collis.ion with nei-ghbouring molecules, a, process called yW!l.aM-ona.-e.. ,~ e l a x a t i c n . Since the SN stat7 is not the lowest electronically excited

' s t a t e ~ ' the molecule ,will ra'pidl d i s s ' i p a t ~ t h e excess e.nergy non-radiativelyJ and cascade to S, t first excited' singlet state. This rapid 'proc.ess

()O-12 sec), as w e l l ~ radiationless transitions ' b ~ t w e e n any ~ ; ~ a ~ e s ' O fthe same multiplicity' (SN ') 0 Sl' 51' -)0 SO' TN +T l ) is called .


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3.tional level of ~ h Sl state.Once the molecule has relaxed to the first excited singlet state

a varie ty of pathways exist ~ o eventual deactivation to SO' Radiationless{ 1 1 . ~ e J r . n a l c.onvelLDion (mentior:ted above) is one possibility. IMVl.btjJ.J:ttm c/r.oMo1gto' a triplet state (net spin angular momentum of one), usually the lowesttriplet state Tl , is second possibility. Deactivation from the excitedtriplet state to So is a "forbidden" transition because of the necessityfor ~ p i ~ i n v ~ r s i o n . As a result, the molecule can r e ~ a i n in the triplet

SO' (li"l.,: \"\.a r o m a t ~ c ' h Y d r O C a r b o n s deactivation of $1 by intersystem crossing to Tl isusually slow (10-6 sec). A third possible decay route from Sl is via aradiative transition to SO' This process involves t h emission of a photonand is referred to as 6 u o J r . ~ c . e n c e . The transition conserves spin multipli-

state for relatively long periods of rme (as long as severa) seconds). Even-tual deactivation may be radiative Involving photon emission re fe rred to as

, \pflOpholr.e6cenc.c, or may involve non-radiative A..n:te!lJ.ltj6:tem c 'lOH


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FIGURE 1. Excited states and p h ~ t o p h y s i c a l processes in a typical organicmolecule. Radiative transitions are given by solid lines;r ~ d i a t i o n l e s s by wavy lines. I.C. internal conversion;I.S.C. intersystem c r o s s i n g ~

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-The molecule D* is referred to as the !.>('n!.>{f..{;:(!'z, and Q as,the


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Photochemistry of Naphthonitrile-Olefin Systerns

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