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7 .825

t L t t

CHLOROPHYLL A

oi

7 815

f f

.. ..

7.410

-

7 405

7.400

;i

c

z

w

7 100

a

n

a

7 090

2

7 470

I , , , , , , , , , , , , ,

HLOROPHYLL B

7.080

3 6 9 I2 15 18 21 24 27

30 36 9

4 2

TI

ME

s e c )

Ejection of protons from chlorophyll-quinoneigure 1.

systems in methanol.

results obtained in air.

on; downward, light off. Top figure: chlorophyll a,

3.7

X M ;

with quinone, 0.03

M .

Bottom figure:

chlorophyll b, 2.3 X l o +

M ;

with quinone, 0.03

M .

Right ordinate represents

The upward arrows represent light

10-6 M . Proton ejection has also been observed in

the present study with the quinone systems

of

pheo-

phytin, bacteriochlorophyll, and hematoporphyrin.

These studies will be reported later.

A possible explanation of the observations is pre-

sented in the following simplified scheme

CHLH

h ,

CHLH*

(1)'

CHLH*

f

CHLH'

(2)

CHLH'(CHLH*)

Q

HL.

Q . -

H +

(3)

where CHLH* and CHLH' are the excited singlet and

triplet s tates of chlorophyll. The interaction of

quinone with either of the excited states of chlorophyll

as in eq

3

is well documented.6 Figure

1

also shows

that the proton ejection activities are of the same order

of magnitude whether air is present or not. This is

surprising since both quinone and oxygen are known

to compete for the excited states of chlorophyll.6

The role

of

the chlorophyll-oxygen in these

light-activated reactions is uncertain. This aspect of

the problem is currently under investigation.

The ejected proton in the present system can originate

from two possible sources: (A) reaction

3

and B) the

solvent, where CHLH. is a cation of a weak base and

Q

is an anion of a strong acid. Studies performed in

the aprotic solvent, dimethylformamide, show that a

proton is ejected as in reaction

3.

In this study a calo-

mel electrode, containing a saturated solution of KC1

in dimethylformamide, was used. The theoretical

behavior of this type of an electrode system has re-

cently been shown by Ritchie and Megerle.1

The results presented in the present paper are not

only important in gaining insight into the mechanism

of the light-activated electron transfer of chlorophyll

systems but also lend support to the current hypothesisll

which relates the dissociation

of

some form

of

chloro-

phyll to the chemiosmotic12 heory of photophosphory-

lation in photosynthesis.

(6) R. Livingston,

Quart.

Rev. (London), 14 174 1960).

7)

E

ujimori and M. Tavla,

Photochem. Photobwl. 5,

877 1966).

8)R. Livingston and K .

E.

Owens, J Am.

Chem.

soc . , 7 8 3301

1956).

9)G

0

chenck, Nuturwissenschuften, 40,205 1953).

10) C.

0

itchie and G. H. Megerle, J Am. Chem.

soc . , 89 1447

1967).

11)H Witt, G . Doring, B. Rumberg, P. SchmidbMende, U.

Siggel, and H. H. Stiehl in Energy Conversion by the Photosyn-

thet ic Apparatus, Publication No. 19,Biology Department,

Brook-

haven National Laboratory, Upton, N. Y., 1967,p 161.

(12) P. Mitchell, Nature , 191 144 1961).

PHOTOCHEMISTRYECTION KENNETH. QUINLAN

ENERGETICSRAN CH EIJI FUJIMORI

SPACE HYSICSABORATORY

L.

G.

HANSCOMIELD

BEDFORD,ASSACHUSETTS 01730

RECEIVED

UGUST

4, 1967

The Intracrystalline Rearrangement

of

Constitutive Water in Hydrogen Zeolite

Y

Sir:

The loss of constitutive or chemical water from

hydrogen zeolite

Y

occurs at temperatures above 500

at torr.'P2 We have found that this reaction occurs

in several minutes, using an inert purge gas at

650

to

750 and approximately 760 torr. The product has

poor thermal stability.

Hydrogen zeolite

Y

heated 2-4 hr at 700-800 in an

inert static atmosphere, where the chemical water

remains in the environs of the hydrogen zeolite, yields

a substance of unusually high thermal stability. This

material remains crystalline on heating to 1000 ,

whereas sodium and hydrogen zeolite

Y

both lose their

zeolite crystal structure at temperatures below

950 .

McDaniel and Maher report the synthesis of a zeolite

Y

of similar high ~t ab i l i ty .~ hey do not define the

critical requirements for its formation nor do they

account for its composition.

1)

H.

A. Szymanski, D. N. Stamires, and G.

R.

Lynch,

J

O p t .

SOC.

Am. 50 1323 1960).

2) J B. Uytterhoeven,

L.

G . Christner, and

W. K.

Hall, J . P h y s .

Chem., 69 2117 1965).

3)C. V. McDaniel and P. K . Maher, preprint

of

paper presented

a t Molecular Sieve Conference, London, April 1967.

Volume 71 Number 2

November

1967

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Scheme I

V

Si

O H

V

Si

0

H

I

4 i-+A1 &Si f 3H20

.f

Si-0-H

H-0-Si

f

Al(0H)a

0

I

Si

m

I

V

Si

H

0

Si

m

I1

V

Si

I

I

0 Al(OH)2@

I

l e

O H

3Si-O-Al &Si f

i-

I(OH):, %-0-Al-0-Si f HzO

I

Si

m

In this stable zeolite, approximately

25

of the

aluminum is present in cationic form.

Clearly this

cationic aluminum is derived from tetrahedrally co-

ordinated aluminum that was initially in the anionic

zeolite framework. About 80-9070 of this aluminum

is exchanged by sodium ion on treatment with 0.10 N

sodium hydroxide solution. The resulting sodium form

of the aluminum-deficient zeolite is also markedly more

thermally stable than the ordinary sodium zeolite Y.

The cause of this increased stability is under study.

This zeolite contains 175 (Si Al) tetrahedra per

unit cell in the anionic framework compared with

192

universally recognized in faujasite. Obviously this

stable material is chemically different from the usual

fau asites.

We propose the mechanism shown in Scheme

I

to

explain the role of chemical water and the formation

of cationic aluminum. Reaction 1 is a hydrolysis in-

volving chemically derived water. Any technique for

keeping this water in the system during the heating

process will result in a stable product.

Reaction 2 is

a neutralization involving the newly formed transient

Al(0H)I and Brgnsted acid sites that still contain

chemical water. The cationic aluminum species in

I

Si

m

I11

structure I11 may react with one or two additional

protons t o yield Al(OH)2+and

A13+.

Studies to be re-

ported later show that cationic aluminum has an aver-

age charge of 1.5, indicating the presence of both Al-

(OH)z+ and A1(OH)2+.

Thermogravimetric studies of the stable material sug-

gest that it contains no chemical water in i ts final form.

Therefore, the four hydroxyl groups in structure I1 are

probably lost as water, resulting in some type of

Si-0-Si bonding. The nature of these sites is not

presently known, but the pronounced contraction of

the unit-cell dimensions

of

this material, relative to

sodium and hydrogen zeolite Y, is probably related to

the formation

of

the aluminum-deficient sites.

Water

derived from these sites and from the proposed hy-

droxylated aluminum cations is available for hydrolysis

of additional Brpinsted acid sites. Details of our

investigation will be reported later.

MOBIL ESEARCHND

DEVELOP M ENTORP ORATION

CENTRALES EARCHIVISIONABORATORY

PRINCETON,EW ERSEY 08540

GEORQE

.

KERB

RECEIVEDUNE23,

1967

The Journal of Physical Chemistry