Correlations of the 0-0 transitions, the absorption and fluorescence maxima with the 6 — Hammett constants

265

JournalofMo~ecukzrStructure,ll4(1984) 265-268 ElsevierSciencePublishersB.V.,Amsterdam-PrintedinTheNetherlands

CORRELATIONS

OF THE O-O

UITtiTHE6-

EAMiElT CONSTANTS

TRANSITIONS, TllE ABSORPTION AND FLUORESCENCE HAXIHA

P.NIKOLO& F. FBdTEti and O.E.POLANSKY' 1 Institute of Organic Chemistry, Bulgarian Academy

of Sciences,

Sofia 1040 (5ulgarJ.a) 2 Max-Planck-IPstitut fur Strahlenchemie. 4330 Mulhein/Ruhr

(PEG)

ISIprevious papers a new approach for the aalysis of correlatiope between electron transitian energies ( Cl-0 transitions. fluorescence and absorption maxiNW this approach is applied to pa) and the 6-H -tt conatancs was developed. NO2 or NH2 - substituted in the phthaloyl ring 3-phenylmztbylene-1(3ti)-isobeozofuranones ( benrylidarephthalides ) - (X,Y)BPHk.

In previous papers (ref.1.2.3) an approach for the analysis of correlations betr=en the absorption 3 (A) and fluorescence$ (F) doa ponding O-O transitions d( 00 ) and the6-Hatt

frequencies, the corres-

constants G(X) based on the prin-

ciple of "linear free energy relationship" was developed. This approach allows to separate the effect of the substit-nt

on the FC trasitions

into two indeperrdeut

contributions: i) change of the energy gap between the groud

and excited state -

jm0);

ii) change of the steepness of the hypersurfaces

of So - a0)

and of S1 -

Z(l).

To avoid repetitions quoting of equations from (ref.l), =e give again the

basic relations:

Ad-d (XI

-d(H)

AL)(A) -Pa x(l)

-p(A)

-p(OO)

i

b&00)

;

A&F)

;

The purpose of the present

x(O)

-p(oo).6(x) -p(F).B(X)

(1)

-p(OO)

(2)

-p(F)

paper is to study

the 3(x>

-G(X)

correlations

for

(X,Y)BPl.i's(see Fig. l), when a donor (D) or acceptor (A) substitrent is inserted iii p' - position of the stilbene subchrowphore,

i.e. ia Y-position of the phtha-

loyl ring.

EESULTS AND DISCUSSICi3 The X and Y substituents in the (X,Y)BPH's investigated and Table 1. The d(X)

-6(x)

are

shovn

in Fig.

1

correlations uere derived cm the basis of absorption

0022-2860/84/$03.00 0 1984 EkevierSciencePublishe~sB.V.

266 TABLE

1

CalcrrlatedP(O0) , a%(O) ad tor (X-A) substituted X

Y

X-D

or la$ (see ~8.

PI?02

()oJ0)

am)

3x1)

1,4

dioxane

+ 6.89

+ 0.41

c 0.45

dioae

- 0.19

Y = l%o2

1,4

- 1.83

+ 0.27

ethanol

+ 4.86

+ 3.71

+ 3.56

A

ethanol

i 1.50

- 0.60

- 0.60

D

Y-?iH

.1.4 diorane

+ 3.58

- 0177

- 0.77

1.4

- 1.04

- 0.11

- 0.11

D

X= X5 X-A

Y - %2

D

X-A

fluarescarce

audethmol.

Influence

of the

traasitiw.

+ 3.92

- 0.62

- 0.75

ethanol

- 2.25

- 0.07

+ 0.07

substituents

has

gap

In nonpolar for YW02,

ethzol

xzd

thence

solvents.

Less

the O-0 is

a characteristic

for all 51x* transitions,

the energy

on

electron

i.e.

of

substituents

least

for Y=H2and

for each

It was

shchm

the substitution

to a decrease the

sad

value.

transition

the energy

on E(O0)

of

conjugated

Cref.21, leads

to a decrease

of the excited wet

in ethanol

than

COP

thatP(OO).&X)

strongly

xx* the

of all is the effect for Y-NIi2 -'Table

of

state,

energy

gap

1. In

Analogously to the umosubstituted

X-BPH's
energies

class

In

alvays

X decrease

such an effect has not been obsemed.

a stronger

- 1.4

for the change of the O-O electron

a mzssure

E(O0) upon substitution,

energy

1).

obtained by us, for solvents with different polarity


By definition

pormdsP
dioxane

ethanol

data,

- dioxzme

CO

in i10s3 CP-~) for donor (X=D) and accep-

Y - NO 2. Y = tie 2

X-A

ad

Val*s

(X,Y)BW's;

SOLVENT

Y - NO2

X==

X=

Z(l)

X-positicu

in

in

X position

dioxzne;

for Y=NI12 have

for Y=N02

the effect

is

reversed. The most significant substituent

effect is observed for X=D and Y=N02

and this is confirmed

by

in

e.g.A

bi02)BPH is about IL.9 D.

for


the

strong

change

the

dipole

m-t

up011 excitation,

r

Steepness of the pot&ial z(n)

charactedze-the

hypersurfaces

in the So and S1 states

changes in the potentialhypersurfaces

a substitution X. A positive
arrincrssle (decrease) of the steepness. Ac=rding

Ad (A) - &UW .6(x) + as<1).6 - p(oo) .6(x) + ae(0).6(x)

as a result of

of the product ~
(1)

md

(2)

(3) (4)

267

Fig.

1.

hear

of O-O transitions (0

correlations

resceslcg < X 1 zu2zima 3 in [10'3.c~'1] vith

), absorption (A

6 (x) - Hmtt

) znd fluo-

constants for (x:,Y)-

disubstituted BPH's in ethanol. Fig. 1-A - Y=NEZ ; Fig. 1,B - Y=Nki2. x - substituents: a=N(~3)2;b'~2;c-OCtij;d=cSt13;e=H;f=F;g=C1; h=cN

; I - NO2 .

Equations

(3)

and

(4)

allov

the

analysis of the hypsochrotic or bathocbronic

shifts of the absorption and fluorescence spectra. Since pC00).6(~)<0, as
AS(A)

vi11 a&o

be negative - the substitllent will cause a batho-

chmraic shift of the absorption ~EILIR. -fae(~).6cx)l< kcrese

I~COO) .6i

of the eneru

ad

gap is mm

if

If Zi1).6@)>0,

tuo cases are possible

l~l>.6(~)1>[pCOO>.6(x)l

, In the first case the

significaut and this vi11 lead

to

a red shift

268 of t&e

iibbsorption-uxixL!nuCaUpon

be observed. IU the enission spectra, diaplace~t

of the flwresace

pm

.6wI

z(o)..~(,~)>o

maxi-

vi11 lead to a bathochromic

If X(O).~(X)CO,

.6(x)) >]Z4b).61

vi11 be observed vhcn IfNO

Ipcooj .6(x)! c

In the'second cese a blue shift will

SubStituti~.

,

a batbocbrouic shift

aad a hypsochrozzic oae, when

.

It follous from :he analysis ofp(OO), i) in all cases the &sage

z
;md z(l)

in the energy gap m

iu Table 1, that:

substitution predominatee

over

the changes of the steepness of the potential hypersurfaces. ii) In 1;4-dioxaae the effect is strongest for the absorption tiua
For
of the

iup (00) is enhsxxed by the decrease

changes least ou substitution, since the aegli-

gible decrease in the.energy of-the

O-O

transition is compensated by the

increase

of the steepuess of the So hypersurfaca. iii) IU ethEno1 the substituent effect where both PC 00 ) and z(1)

is strongest for AS(A) of (D,NO~)BPH'S,

iuflrrence stroagly and iu the same direction the energy

of the trausitioa. The veakest effect

is

observed for

A $ (F) of (A,N02)BP?i's. where

the tvo factors have a weak influence and act in different directions. For (A&$) BPLi's the bathochrordc shift of the absorption and fluoresceace is equal al)

because

- - z(O).

Elm?EEENcEs

1 2 3

O.E. Polansky, F. Fratev ;md P, Nikolov, Z. Naturforsch., 36a (1981) 197-202. F. Fratev, P. Nikolov and O.E. Polsnsky, Z. Naturforsch., 37a (1982) l341-1347. P. Nikolov. F. Fratev and S. Fiinchev, Z. Naturforsch., 38a (1983) 200-205.