Sedimentary Porphyrins: Unexpected Structures, Occurrence, and

Chapter 2 Sedimentary

Porphyrins:

Unexpected

Structures,

Occurrence, and Possible Origins M. Inês Chicarelli, Surinder Kaur, and James R. Maxwell

Downloaded by CORNELL UNIV on May 17, 2017 | http://pubs.acs.org Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

Organic Geochemistry Unit, University of Bristol, School of Chemistry, Cantock's Close, Bristol BS8 1TS, United Kingdom

The occurrences of sedimentary porphyrins whose structures have been fully or partially established are reviewed. The compounds range from components with carbon skeletons providing clear evidence of specific precursor chlorophylls to those which are not obviously related to known biological pigments. Three examples from the latter category are reported: a C component from Serpiano o i l shale (Triassic, Monte San Giorgio, Switzerland), containing a fused ring system, and two components (C , C ) from Gilsonite bitumen (Eocene, Utah, U.S.A.), containing a methyl-substituted, five membered exocyclic alkano ring. In addition, evidence is presented that Boscan crude o i l contains extended (> C ) monobenzoporphyrins. 34

32

33

33

In m o l e c u l a r selected before

organic

members

geochemistry,

assignment

of the s t r u c t u r e s of

o f any c l a s s o f b i o l o g i c a l

markers

i s essential

t h e d i s t r i b u t i o n s o f t h e c l a s s i n q u e s t i o n can be used i n an

a p p l i e d sense. Such assignments i n v o l v e e i t h e r s y n t h e s i s o f s u s p e c t e d compounds and c o i n j e c t i o n mass s p e c t r o m e t r y ) isolation (e.g.

with

of individual

using

nuclear

crystallography). compounds then

A

(e.g. using

a sedimentary components magnetic

knowledge

provides

combined

gas chromatography-

fraction

c o n t a i n i n g them, o r

and d i r e c t

resonance

structure analysis

spectroscopy

of the d e t a i l e d

or

structures

a b a s i s f o r : ( i ) understanding

X-ray

of the

the o r i g i n s

and d i a g e n e t i c pathways i n v o l v e d i n t h e i r f o r m a t i o n , ( i i ) u s i n g

0097-6156/87/0344-0040$08.00/0 © 1987 American Chemical Society

Filby and Branthaver; Metal Complexes in Fossil Fuels ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

their

2.

CHICARELLI ET AL.

distributions

41

Sedimentary Porphyrins

f o r correlation

and m a t u r a t i o n

studies,

and

in

p r o v i d i n g i n f o r m a t i o n about d e p o s i t i o n a l environment. To

date,

most

o f the

developments

b i o l o g i c a l marker geochemistry

i n , and a p p l i c a t i o n s

of,

have been a s s o c i a t e d w i t h s t e r o i d s and

t r i t e r p e n o i d s ; t h i s r e s u l t s from a f a i r l y d e t a i l e d knowledge o f t h e i r o r i g i n s and

g e o l o g i c a l f a t e ( 1 ) . D e s p i t e the f a c t t h a t the

of sedimentary these

compounds

geochemical vanadyl


p o r p h y r i n s was r e c o g n i s e d

have

n o t been

very

occurrence

i n the e a r l y

extensively

used

1930's,

i n applied

s t u d i e s . They occur w i d e l y and m a i n l y as n i c k e l - I I and/or

complexes

restricted for

alkyl

( 2 ) , although

occurrences

example

complexes

o f other

manganese-II,

i n coals

generally smaller metal

iron-Ill

c h e l a t e s have (3,4)

and c o p p e r - I I

amounts and more been

reported,

and g a l l i u m - I I I

complexes

(5_>^0

i n immature

oceanic

sediments (7,£). Free base s p e c i e s have a l s o been d e t e c t e d i n o c e a n i c sediments

(9-11)

availability effectively these

and s h a l e s

of efficient

(12,13).

HPLC and ~~*H

In

recent

NMR t e c h n i q u e s

years, the

has c o n t r i b u t e d

t o the s t r u c t u r e e l u c i d a t i o n o f i n d i v i d u a l components o f

complex

mixtures.

HPLC,

used

on an a n a l y t i c a l

scale

(14),

a l l o w s the d i s t r i b u t i o n t o be o b t a i n e d e f f i c i e n t l y and r o u t i n e l y , and the i s o l a t i o n

o f mg amounts o f i n d i v i d u a l

components i n h i g h

purity

when used on a p r e p a r a t i v e s c a l e under normal (15) o r r e v e r s e d phase (16,17) c o n d i t i o n s . "^"H NMR, i n c o n j u n c t i o n w i t h s t u d i e s , has

now become the most i m p o r t a n t

n.O.e. d i f f e r e n c e

and w i d e l y used method o f

s t r u c t u r e assignment. Since

the

first

full

assignments, a

a e t i o p o r p h y r i n s , a C^y ( D partial an

determination

e x o c y c l i c alkano

from

a variety

studies

have

exocyclic

the

concerned

ring,

which

or partly In relation

pigments, these whose

after

carbon

precursors,

(b)

can

mainly

five

have

to origins

probably

an

components. Indeed, the p o r p h y r i n s have now

I , I I and r e f e r e n c e s

related

biological

to selected

skeletons

can

types

of

be r e l a t e d t o

o n l y be r e l a t e d

(d) compounds whose carbon

obviously related

having

of structural

f o u r c a t e g o r i e s : (a) compounds

s p e c i f i c p r e c u r s o r s , (c) compounds which can at p r e s e n t

variety

i n terms o f p r e c u r s o r

compounds whose carbon

s p e c i f i c p r e c u r s o r s , and

(8) w i t h

e l u c i d a t e d . These

components

a wide

(Tables

be d i v i d e d i n t o c a n be

been

with

sedimentary

established

skeletons

C-^ component

s t r u c t u r e s o f a number o f compounds

exhibit

thirty

d e m e t a l l a t i o n , o f two

(2) component (1£>1^)> and the

more r e c e n t l y w i t h f u n c t i o n a l i s e d

fully

therein).

£32

a

o f g e o l o g i c a l samples

s t r u c t u r e s o f more than been

d

(20) o f a d e m e t a l l a t e d ring,

been

alkano

t y p e s , and

n

t o non-

s k e l e t o n s are

not

t o known p r e c u r s o r s . In a d d i t i o n , i t i s

u s e f u l t o d e f i n e another

category

( e ) , c o m p r i s i n g compounds

of a type whereby the s t r u c t u r e which o c c u r s n a t u r a l l y may have been


42

M E T A L C O M P L E X E S IN FOSSIL F U E L S

Table

I.

Reported

Occurrences of Individual Alkyl Sedimentary Organic Matter

Occurrence (Structure )

a(l-4,8,9,12 ,13 )

18-21

b(5,8,9,ll,14)

22-24

c(2,8)

25

d(2,4,6,8-10)

26-28

e(7,8**,10**)

29

f(9)

30

g(2**)

4


§

Porphyrin

Reference

§

Porphyrins

Structural (Structure )

in

Type

8-14

15-17

18,19

20,21

b(25 ) §

h(22)

i(23,24)

*

Present

reported +

Occurrence:

shale: N.E.

England;

Parachute and c o a l s , El

Ni(ll)

e)

d)

Monte

Julia

Messel

Creek,

V=0 c o m p l e x e s

(unless

Creek

o i l shale:

o i l shale:

Green

shale:

Basin,

Eocene,

San G i o r g i o ,

River

Eocene,

formation,

see 4 (and r e f . t h e r e i n ) .

Lajjun

Maracaibo

stated

otherwise);

metal not

Uinta

Cretaceous, near Uinta

c)

Basin,

Jordan;

Utah, Marl

Toolebuc

Darmstadt,

In t h i s c a s e ,

Upper-Cretaceous,

Basin,

Switzerland;

USA;

W. Germany;

Utah, Boscan

Permian

formation,

USA; g)

2 characterised i)

b) S e r p i a n o o i l

Slate:

crude

f)

presented

A s s i g n m e n t by c o m p a r i s o n w i t h

i n this

Abelsonite:

several

as F e ( I I I )

lignites complex;

o i l : Cretaceous,

paper.

literature

shale,

Queensland,

Venezuela.

§ Structural studies **

and/or

a) G i l s o n i t e bitumen:

Mid-Triassic,

Australia;

h)

as

for simplicity.

H NMR s p e c t r u m .


CHICARELLI ET AL.

Table

II.

43


Reported

Occurrences of Individual Functionalised in Sedimentary Organic Matter

Occurrence*

Reference

Porphyrin


(Structure)

Structural

Porphyrins

Type

(Structure)

e(26-29,31-35) 9(30)

e(36) c(37,38)

36

*

Reported

as N i ( I I )

characterised + Occurrence:

as

complexes

Fe(III)

only,

and

c , e and g , s e e T a b l e

with

Ga(III)

37,38

the exception complexes

(38

of

30 w h i c h

and

ref.

h a s been therein).

I


44


chemically

modified

purification

i n some

procedures.

way as a r e s u l t

Careful

compounds which

may be c a n d i d a t e s

order

confusion

t o avoid

naturally

components occur

for this

between

i n t h e sediment

and a

compounds w i t h i n each c a t e g o r y the

attention a

of the i s o l a t i o n or has

to

category

diagenetic

be

paid

reaction occurring

laboratory reaction.

Examples o f

a r e g i v e n as f o l l o w s . Although

as N i ( I I )

and/or

V=0 complexes

o t h e r w i s e ) , they a r e l i s t e d as t h e f r e e base f o r

to

(artefacts) i n

a l l of

(unless stated

convenience.

Compounds r e l a t e d t o s e l e c t e d p r e c u r s o r types ( T a b l e s I , I I )


This category

i n c l u d e s d e o x o p h y l l o e r y t h r o e t i o p o r p h y r i n ( 8 ) i t s e l f and

i t s C-^ c o u n t e r p a r t sedimentary

alkyl

( 9 ) , which appear t o occur almost

ubiquitously i n

p o r p h y r i n m i x t u r e s and a r e p r o b a b l y

[as the N i ( I I )

and V=0 complexes] t h e two most abundant p o r p h y r i n s i n t h e geosphere, the q u a n t i t i e s p r o b a b l y

f a r outweighing

any b i o l o g i c a l

pigment. They

have been proposed as a r i s i n g from d e f u n c t i o n a l i s a t i o n o f c h l o r o p h y l l £

on t h e b a s i s o f i t s h i g h

s h o u l d be n o t e d , be

additional

precursors

pathways. S i m i l a r (10)

relative

abundance i n t h e b i o s p h e r e . I t

however, t h a t o t h e r c h l o r o p h y l l s ( e . g . 41,42) c o u l d and c o u l d

undergo

compounds i n t h e c a t e g o r y

analogous

degradative

i n c l u d e t h e C-^g analogue

o f 8 and 9 and t h e c a r b o x y l i c a c i d s 26-29,31,32. Other

alkyl

p o r p h y r i n examples a r e r e p r e s e n t e d by a w i d e l y o c c u r r i n g C-^g mono /5H aetioporphyrin 17),

and

(18,19).

( 5 ) , t h e C^*

the In t h e case

and

C31

a

C-^

o f 15-19,

n

d ^39 15,17-butanoporphyrins

(15-

(15^-methyl)-15,17-propanoporphyrins i t has been

proposed

e x o c y c l i c a l k a n o r i n g has formed by way o f a c o n d e n s a t i o n a f u n c t i o n a l i s e d i n t e r m e d i a t e on t h e d e g r a d a t i v e pathway

that the r e a c t i o n of

(23,31-33).

Compounds r e l a t e d t o s p e c i f i c p r e c u r s o r s (Table I , I I ) The carbon s k e l e t o n o f a C-^ mono /5H-13,15-ethanoporphyrin ( 1 1 ) , p r e s e n t i n S e r p i a n o o i l s h a l e m a i n l y as t h e vanadyl complex, has been suggested (24) as a r i s i n g from d e g r a d a t i o n o f c h l o r o p h y l l ID ( 4 0 ) . The o c c u r r e n c e i n Messel s h a l e o f components w i t h a m e t h y l - s u b s t i t u t e d f i v e membered e x o c y c l i c r i n g (20,21) and r e l a t e d a c i d (36) l e d t o t h e s u g g e s t i o n (16,34) o f a d i a g e n e t i c a c i d c a t a l y s e d rearrangement o f an i n t e r m e d i a t e from c h l o r o p h y l l c ( 4 1 ) , which o c c u r s o n l y i n c e r t a i n types o f a l g a e . F u r t h e r e v i d e n c e of a m i c r o b i a l input t o t h i s immature s h a l e by way o f p h o t o s y n t h e t i c b a c t e r i a came from t h e d i s c o v e r y o f t h e h i g h e r ( C - ^ t o C ^ ) p o r p h y r i n a c i d s (33-35; 17). I n t h i s c a s e , t h e r e i s c l e a r e v i d e n c e t h a t t h e sedimentary p r o d u c t s have a r i s e n from b a c t e r i o c h l o r o p h y l l s d ( 4 3 ) .


2.

CHICARELLI ET AL.

45


Compounds r e l a t e d t o n o n - s p e c i f i c p r e c u r s o r s ( T a b l e s I , I I ) Compounds o f t h i s type a r e perhaps best r e p r e s e n t e d by c e r t a i n o f the aetioporphyrins.

Aetioporphyrin

opening

a t some stage i n t h e d e g r a d a t i v e pathway o f the f i v e membered

equally

ring

i n the precursor

apparent,

decarboxylation acid

whose

a ( 3 9 ) , or other

however,

NMR spectrum

indistinguishable

from

or a degradative

that

o f mesoporphyrin

H

chlorophylls,

i t could

product.

have

IX [ 3 0 , i r o n ( I I I ) has been

diagenetic

product

o f cytochromes,

many micro-organisms)

i s

from A di-

properties

isolated

were

as t h e F e ( I I I ) c o u l d be a

s i n c e most organisms

c o n t a i n cytochromes w i t h

It

arisen

complex].

and chromatographic

the l a t t e r

by way o f

complex from c o a l s , and i t was proposed t h a t t h e d i - a c i d Downloaded by CORNELL UNIV on May 17, 2017 | http://pubs.acs.org Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

(19) a s

from

exocyclic

chlorophyll

I I I (2) has been suggested

arising

(including

s u b s t i t u t e d mesohaem

p r o s t h e t i c groups ( 4 ) . Compounds not o b v i o u s l y r e l a t e d t o known p r e c u r s o r s (Table I ) Two r e c e n t examples e x e m p l i f y so-called

rhodoporphyrins

t h e problem. D e s p i t e t h e f a c t t h a t the

have

been

w i d e l y i n sediments and p e t r o l e u m s , that

t h e two major

porphyrins

(23,24).

exocyclic envisage,

ring

rhodoporphyrins These

found

however,

contain

i n a l l chlorophylls; the suggestion

t o occur

i n Boscan o i l a r e monobenzo[g]-

components

how t h e benzene

c h l o r o p h y l l , although

known f o r many y e a r s

o n l y r e c e n t l y has i t been shown

ring

the five

membered

i t i s difficult

could

arise

of a bacterial

from

origin

to

a known has been

made ( 3 6 ) . Components p o s s i b l y of a r t e f a c t o r i g i n (Table I I ) The

isolation

o f two p o r p h y r i n a l c o h o l s (37,38),

component 37 b e i n g

the h y d r o x y l a t e d c o u n t e r p a r t o f the most abundant a l k y l p o r p h y r i n i n the geosphere, r a i s e s t h e p o s s i b i l i t y the

isolation

possibility exocyclic

procedure

comes ring

from

position

used

t h a t they might be a r t e f a c t s o f

to obtain

the reported

them from

Marl

hydroxylation,

o f a synthesised

slate.

This

a t t h e same

(13^-methyl)-13,15-ethano

p o r p h y r i n when chromatographed on s i l i c a ( 4 0 ) . Present

Study

Apart from reviewing t h e occurrences p o r p h y r i n s r e p o r t e d t o o u r knowledge,

of individual we r e p o r t here

sedimentary structural


46

M E T A L C O M P L E X E S I N FOSSIL F U E L S

s t u d i e s o f t h r e e sedimentary

a l k y l p o r p h y r i n s which

appear t o b e l o n g

t o c a t e g o r y (d) as a r e s u l t of t h e i r unusual s t r u c t u r e s , although the p o s s i b i l i t y of t h e i r being artifacts i s also considered. The t h r e e 1 2 components a r e : ( i ) a C-^ (13 -methyl)-13,15-ethano-13 ,17-prop13 (15 )-enoporphyrin

from

S e r p i a n o o i l s h a l e ( c f . Table

I),(ii) a

C-^ and a C-^ (13^-methyl)-13,15-ethano-porphyrin from Gilsonite bitumen (cf_. Table I ) . In a d d i t i o n , p r e l i m i n a r y e v i d e n c e i s p r e s e n t e d that (cf.

the Boscan o i l shown r e c e n t l y t o c o n t a i n monobenzoporphyrins Table I ) c o n t a i n s h i g h e r m o l e c u l a r weight components o f t h i s

t y p e , adding

f u r t h e r c o m p l e x i t y t o u n d e r s t a n d i n g the o r i g i n o f t h e s e


o t h e r c a t e g o r y (d) compounds.

Experimental 1. Methods: Low r e s o l u t i o n mass s p e c t r a were o b t a i n e d , u s i n g the d i r e c t

insertion

probe, on a F i n n i g a n 4000 s p e c t r o m e t e r c o u p l e d t o an INC05 2300 d a t a system.

C o n d i t i o n s : e m i s s i o n c u r r e n t 350uA; i o n i s a t i o n

v o l t a g e 40eV,

s o u r c e 250°C and probe programmed from 90° t o 300°C. High s p e c t r a were r e c o r d e d on a VGMS9 s p e c t r o m e t e r system.

Conditions: ionisation

coupled

v o l t a g e 70eV, s o u r c e

resolution

t o a VG

data

200°C and probe

programmed from 50° t o 250°C; r e s o l u t i o n 10,000; p e r f l u o r o k e r o s e n e as internal reference. H NMR

s p e c t r a l d a t a f o r the i n d i v i d u a l p o r p h y r i n s , as z i n c ( I I )

c h e l a t e s , were o b t a i n e d on a JE0L

and/or

on a

Bruker WH 400 i n s t r u m e n t . Samples were examined i n (CD^)^CfJ/5%

FX200 FT

instrument

C^D^N

or C D /55o C^D^N. C o n c e n t r a t i o n s were t y p i c a l l y 6

of

decoupling

previously High system

using

and

n.O.e.

a

liquid

Spectra

LDC

150

solvents

s t u d i e s have

chromatography

P h y s i c s SP8700

and Rheodyne 7125 i n j e c t o r . an

Analytical each

experiments

. Details

been d e s c r i b e d

(22-24). performance

performed using

2-4mg ml

6

1202

Spectromonitor

runs were performed x

4.6

mm)

connected

(HPLC)

analyses

ternary solvent

Detection

(400 nm) was

II variable

wavelength

were

delivery obtained detector.

u s i n g t h r e e columns ( S p h e r i s o r b i n series,

using

a

S3W;

combination

of

as d e s c r i b e d i n 14. The p r e p a r a t i v e - s c a l e c o n d i t i o n s were

similar,

except

programme

that

there

were

minor

( 1 5 ) , and the a n a l y s e s were

column (250 x 10 mm).

changes

performed

in on

the

solvent

Spherisorb

The components o b t a i n e d were demonstrated

>95% pure by a n a l y t i c a l

HPLC.


S5W

t o be

2.

CHICARELLI ET A L .

2.

Isolation:

The

isolation

47


o f rhodoporphyrins

described previously

from

Boscan

crude

o i l has been

( 3 6 ) . The t o t a l m e t a l l o p o r p h y r i n s were e x t r a c t e d

from S e r p i a n o o i l s h a l e and G i l s o n i t e bitumen a s d e s c r i b e d p r e v i o u s l y (22,23;18).

The i n d i v i d u a l

compounds o b t a i n e d by p r e p a r a t i v e - s c a l e

HPLC were c o n v e r t e d t o t h e i r

z i n c ( I I ) c h e l a t e s and p u r i f i e d

( S i Q ^ g e l G, 5% a c e t o n e / t o l u e n e ) . V o l a t i l e under high-vacuum

(generally

NMR a n a l y s e s . G e n e r a l

impurities

were

by TLC removed

100°C; 10 ^ T o r r ; c a . 5h) p r i o r

spectroscopic properties

to H

o f 2 5 , 12, 13

are

summarised as f o l l o w s : 1

a)

(13 -methyl)-13.15-ethano-3,8-diethyl-2,7,12,18-tetramethyl2

2

13 ,17-prop-13 (15^)-enoporphyrin Downloaded by CORNELL UNIV on May 17, 2017 | http://pubs.acs.org Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch002

C

H

N

r e c

(25):

HRM5:

found

500.2952,

u i r e s

34 36 4 l 500.2944; EIMS(40eV) s i g n i f i c a n t i o n s : 500 ( 1 0 0 % ) , 485 ( 1 9 ) , 250 ( 2 0 ) ; u v / v i s ( C H C 1 ) : X = 512, 548, 582, 639nm; z z i max 9

9

r e l . i n t . 100:17:33:13, Soret 416nm;

H NMR, see t e x t .

1

b)

(13 -methyl)-13,15-ethano-8,17-diethyl-2,3,7,12,18-pentamethyl-

porphyrin EIM5

(12):

HRM5: found

(40eV) s i g n i f i c a n t

ions:

H

476.2946, C 2 3 3

N 6

4

requires

476.2940;

476 ( 1 0 0 % ) , 461 ( 3 5 ) , 448 ( 1 5 ) ,

238

(40) ; u v / v i s ( C H C 1 ) : A = 500, 533, 564, 618nm (IV>11>I>111), 1 z z max Soret 400nm; H NMR, s e e t e x t . c) ( 1 3 - m e t h y l ) - 1 3 , 1 5 - e t h a n o - 3 , 8 , 1 7 - t r i e t h y l - 2 , 7 , 1 2 , 1 8 - t e t r a m e t h y l 9

9

X

1

porphyrin (13):

EIMS (40eV) s i g n i f i c a n t

i o n s : 490 ( 1 0 0 % ) , 475 ( 2 5 ) ,

(40); uv/vis ( C H C 1 ) : A = 500, 532, 565, 618nm ( I V > I I > I > I I I ) , i z z max S o r e t 400nm; H NMR, s e e t e x t . Structural Studies

245

1.

9

9

1

(13 -methyl)-13,15-ethano-3,8-diethyl-2,7,12,18-tetramethyl2

2

13 ,17-prop-13^(15 )-enoporphyrin This mainly

C^H^N^

species

was i s o l a t e d ,

a s t h e V=0 complex),

performance

liquid

corresponds

formally

spectrum i s markedly

(25):

from

chromatography. to a

after

d e m e t a l l a t i o n (present

Serpiano

o i l shale

Although

the molecular

rhodo-type

component,

using

high weight

the electronic

d i f f e r e n t from t h a t expected f o r such a s p e c i e s

(41) . The H NMR spectrum o f t h e Z n ( I I ) complex ( F i g u r e 1; Table I I I ) i n d i c a t e d t h e presence o f 4 /5-methyls, 2 / J - e t h y l s , 1 CH^CH-moiety, 3 meso-H's, 1 o l e f i n i c - H and 2 more - C H 2 - s i g n a l s ( s e e 42 f o r p r e l i m i n a r y r e p o r t ) . Based on t h e r e s u l t s o f t h e s e l e c t i v e d e c o u p l i n g e x p e r i m e n t s , t h e e x o c y c l i c r i n g moiety below c o u l d be proposed:

American Chemical Society. Library

115516th St., N.W. Washington, 20036 Filby and Branthaver; Metal D.C. Complexes in Fossil Fuels ACS Symposium Series; American Chemical Society: Washington, DC, 1987.


48


10

'

9

7

'

6

'

5

4

2

3

8 (ppm)

Figure

1

1. 200 MHz H NMR

1

spectrum o f ( 1 3 - m e t h v l ) - 1 3 , 1 5 - e t h a n o 2

2

3,8-diethyl-2,7,12,18-tetramethyl-13 ,17-prop-13

(15 )-enoporphy-

rin

indicate

( 2 5 , as

enhancements

zinc

complex)

observed;

i n CDCly

dotted

arrow

Arrows

indicates

weak

observed.


n.O.e. n.O.e.

2.

CHICARELLI ET AL.


Table

200

III.

MHz

49


l

H

NMR

da ta

component

for

n ..0 . e .

2 5• ( a s

*

zinc

Code

complex)

i n CDCl-j

A s s i gnment

S(ppm)

Multiplicity

9 . 46

s

n .d .

meso-Ha

H-20

9 . 43

s

n .d .

meso-Hb

H-10

9 . 31

s

3 . 39

meso-Hc

H-5

6 . 73

dd

no i n . 0.6 >.

CH-A

CH-15

4 . 93

bq

2 . 06

CH-B

, , 1 CH-13

• *

3 .9 6 3. 9 0

m

§

9

I *

m

§

h.

43,

9 ., 3 1 ,

3.43

39,

3 ., 2 7 ,

1.70,

3 . 54

d

9. 43,

3. 43

s

n .d .

3 . 3 9§

s

9. 46,

3 . 2 7§

m

n .d .

d

4. 93,

2 ., 0 6 1 ., 7 0

+

+

t

1. , 6 8

+

+

t

*

Chemical

used

in

although 2d),

observed

+

shifts

Figure

where

1

CH-jCH-B

9 ,. 3 1 ,

confirmed

(x2)

2

CH -18

3

3

and d

seen

§ Partially

by d e c o u p l i n g . s = singlet,

when

8

CH CH-B

Ch^CH-13

CH CH 3

2

CH CH -8

CH CH

2

CH CH -3

signal

overlapping

3

irradiated. * * Weak

irradiation

t = triplet,

q =

1

2

3

signals.

++ S i m u l t a n e o u s

d = doublet,

3

?

3

3.90, 3.39

CH -2,7 CH -15^

2

9 • 31,

2

CH -12

CH-j-c

3 .54

3

CH -b

3

ca. 3.94

4

CH CH -8,3

CH -a

CH -D

enhancements

n . d . r not determined,

m = multiplet,

3

2 ,. 0 6

3

and 2 .

2

2

CH CH

3

43,

9

(I -

CH -15

CH -C 1.68

2

1

2

+

Codes

n.O.e., (Figure quartet,

b = broad.



50


D The n.O.e e x p e r i m e n t s l i s t e d i n Table I I I were performed under low power i r r a d i a t i o n t o a l l o w good f r e q u e n c y s e l e c t i v i t y . Some o f them a r e d i s c u s s e d as f o l l o w s ( s e e a l s o F i g u r e 2 ) : ( i ) i r r a d i a t i o n o f CH^-a a t 3.54 ppm caused an enhancement i n meso-H^ a t 9.43 ppm and i n the CH-j d o u b l e t (2.06 ppm), t h u s p r o v i d i n g e x t r a e v i d e n c e f o r the p o s i t i o n o f CH^-a i n r e l a t i o n t o t h e e x o c y c l i c r i n g moiety ( F i g u r e 2 a ) ; ( i i ) i r r a d i a t i o n o f t h e two o v e r l a p p i n g t r i p l e t s (CH^Cr^'s) a t c a . 1.69 ppm enhanced t h e s i g n a l s o f the CH-^Cr^'s, as w e l l as o f t h e o v e r l a p p i n g CH-^-c and CH^-d ( b o t h were enhanced, as i n d i c a t e d by the i n t e n s i t y o f t h e n.O.e.) and t h e meso-H's a t 9.31 (H ) and 9.43 (H. ) —

ppm

(Figure

2d); similar

(r7,Z7,32);

(iii)

irradiation

of

C

connections

irradiation

have

been

a t c a . 3.94

the p a r t i a l l y

overlapping

ppm

D

observed

before

( i . e . simultaneous

CH^CH^

(x2) and

Ch^-C

s i g n a l s ) r e s u l t e d i n enhancements o f t h e s i g n a l s from meso p r o t o n s H and H

c

(9.31 and 9.43 ppm), CH -b (3.43 ppm), CH »s c and d (both a t

b

3

3.39 ppm), CH ~D 2

triplets

(3.27 ppm)

(CH-jCh^'s)

experiment ( i i ) ,

3

and o f t h e two p a r t i a l l y

a t c a . 1.69 ppm

(Figure

overlapping

2 c ) . B e a r i n g i n mind

t h e enhancements o f t h e two m e t h y l s (c + d ) , t h e two

meso-H's and t h e two t r i p l e t s were a t t r i b u t e d t o c o n n e c t i o n s w i t h t h e two methylenes CH^-D

were

a t 3.90 ppm, w h i l e

attributed

eliminate p o s s i b i l i t i e s the

to

These

results

o f s t r u c t u r e s w i t h two e t h y l groups

flanking

same meso-H, o r w i t h

ring;

(iv) irradiation

t h e enhancements o f t h e CH-^-b and

irradiation

two e t h y l s

o f meso-H

of

CH -C. 2

a t t a c h e d t o t h e same

pyrrole

a t 9.31 ppm c o n f i r m e d t h e s p a c i a l

c o n n e c t i o n s w i t h CH^-c ( o r d) and a CH-^CH,^ group. Thus, s t r u c t u r e examined

25 c o u l d

be a s s i g n e d . The component

was

by mass s p e c t r o m e t r y under c h e m i c a l i o n i s a t i o n , u s i n g H

reagent g a s ; the spectrum

i s compatible with

the proposed

also 2

as

structure

(23). 1

2. ( 1 3 - m e t h y l ) - 1 3 , 1 5 - e t h a n o - 8 , 1 7 - d i e t h y l - 2 , 3 , 7 , 1 2 , 1 8 - p e n t a m e t h y l p o r p h y r i n (12) and C-^ c o u n t e r p a r t ( 1 3 ) : These components, i s o l a t e d as t h e f r e e bases from G i l s o n i t e bitumen, i n which they o c c u r as the N i ( I I ) complexes, where examined by NMR


CHICARELLI ET AL.


51


2.

F i g u r e 2. Examples o f n.O.e. e x p e r i m e n t s performed on component 25 ( a s z i n c complex) i n C D C l y The i n s e r t i n (a) shows t h e expanded meso-H r e g i o n o f t h e normal spectrum; i n ( c ) they show expanded r e g i o n s o f t h e normal spectrum ( t o p ) and o f t h e n.O.e. d i f f e r e n c e spectrum ( b o t t o m ) . Arrows i n d i c a t e n.O.e. enhancements observed. A s t e r i s k i n d i c a t e s point of i r r a d i a t i o n .


52

M E T A L C O M P L E X E S IN FOSSIL FUELS

at 200

and 400

MHz

i n two d i f f e r e n t

solvents

[(CD ) C0/5£ C ^ N 3

and

2

C^D^/5% C^D^N]. The s p e c t r a of 12 ( e . g . F i g u r e 3) showed the presence of 5 0 - m e t h y l s , 2 0 - e t h y l s and the e x o c y c l i c I V ) . The

ring

was

3 meso-H's. The

determined

by

-CH^HChy- moiety i n

decoupling experiments (Table

a p p r o p r i a t e n.O.e. s t u d i e s were performed and the r e s u l t i n g

c o n n e c t i o n s between / J - s u b s t i t u e n t s and meso-protons The very

H NMR

similar

absence

to

of

the

C-^

a t ca_.

4.12

2

and

not shown] were

c o u n t e r p a r t 12,

1.94

ppm ppm

except

f o r the

(CH^-3) which was

replaced

( C H C H ~ 3 ) . In summary, the 3

2

c o n n e c t i o n s between the 4 ^ - m e t h y l s , 3 / S - e t h y l s , 3 meso-H's and

the

-CH CHCH -

12,

2


those

of the resonance a t c a . 3.56

by resonances

were e s t a b l i s h e d .

s p e c t r a of 13 [as z i n c ( I I ) complex;

moiety

3

establishing

the

were

obtained

compound

as

in

the

same

way

as

for

(13^-methyl)-13,15-ethano-2,8,17-tri-

e t h y l - 2,7,12,18-tetramethylporphyrin. It

is

noteworthy

that

the

C^

compound

2

(12)

was

isolated

p r e v i o u s l y from G i l s o n i t e bitumen and the s t r u c t u r e g i v e n as 44 ( 4 3 ) . U n f o r t u n a t e l y , t h a t sample

was

isolated

p u r i t y and q u a n t i t y ; a l s o , the CH^ a residual

p r o t o n resonance

f o r ^"H NMR

a t C-13

[ v i z . of

1

studies

i n lower

i s masked i n (CD-^CO by

(CH-^CO i m p u r i t y ] and

l e d to

assignment of the methyl s u b s t i t u t e d , f i v e membered e x o c y c l i c r i n g a s i x membered than

one

ring.

solvent

T h i s emphasises

f o r "^H

NMR

the

importance

analyses of

f o s s i l p o r p h y r i n s which can be i s o l a t e d

the

of

small

using

quantities

oil:

A sequence

on

of p r o c e d u r e s

allowed

and

isolation

involving

HPLC u s i n g of a

flash

normal

variety

of

of

conveniently.

3. High m o l e c u l a r weight b e n z o p o r p h y r i n s from Boscan crude

demetallation

as

more

and

chromatography r e v e r s e d phase

fractions

enriched

silica,

conditions

i n porphyrins

showing rhodo-type c h a r a c t e r i s t i c s (36; see a l s o r e f e r e n c e s t h e r e i n ) . Reversed phase

HPLC then a f f o r d e d

the two

t y p e , which were a s s i g n e d i n the u s u a l way having

structures

rhodo-type

23

uv/visible

and

24

was

C^g,

m o l e c u l a r weight with

molecular

monobenzoporphyrins

benzene

ring,

(>

ions

a

fraction

(Figure t o be

4a).

corresponding

with

clear

that

suggesting i n d i r e c t l y

beyond C-^ are a l s o monobenzoporphyrins

from

the C-^ that

the

this

a

concentrated i n

C-^^), e x t e n d i n g t o

components i s o l a t e d

i t i s already

this

Electron at

least

formally

w i t h an e x o c y c l i c a l k a n o r i n g ( F i g u r e 4 b ) .

s t u d i e s of i n d i v i d u a l p r o g r e s s but

obtained

the f r a c t i o n

components

components o f

monobenzo[g]porphyrins,

( 3 6 ) . In a d d i t i o n ,

spectrum

impact mass s p e c t r o m e t r y showed higher

major as

fraction

to H

NMR

are i n

component c o n t a i n s

a

components e x t e n d i n g

(44).



1

'

1

' I '/ 102

l

/ > » • i • • ' |' • ' 5b 1

' ' 1

1

6

6

b (ppm)

' • '' |' ' ' • 50 1

' ' ' ' ' » ' ! '' 45

1

3

2

• ' '' ' ' ' • ' I 40

1

» '

1

' ''' ' ' ' 35

1

Figure 3. 400 MHz H NMR spectrum of (lS^methylJ-l 3,15-ethano-8,17-diethyl-2,3,7,l 2,18pentamethylporphyrin (12, as zinc complex) in C D /5% C D N; arrows indicate n.O.E. enhancements observed. Inserts: (a) expansion of the exocyclic ring protons; (b) alter irradiation of C H C H at 4.118 ppm to decouple the C H C H at 1.937 ppm.

1

I • • • • ' I 104 103


[/ 20

/

1

i 18

' f 16

' i


Table

IV.

400

MHz

H NMR

data

for

component

C D /5£ 6


S

(ppm)

Multiplicity

12

5

*

n.O.e.

s

1 0 ., 323

s

3. 6 8 7 ,

( 3.628 ,

1 0 ., 2 1 5

s

3 ., 5 6 4 ,

3.556

dd(o

A B

4 ,. 9 1 9

dd(3

B C

( 3 . 687 ) , §

16 . 6 , 6. 4,

3

4 . 502

BC m

4.919

zinc

complex)

+

3.628,

Assignment

meso

3.590 3.590 )

8

H-20

meso

H-10

meso

H-5

4 ., 9 1 9

CH (A)-13

2

n ., d .

CH (B)-13

2

2

4.502)

16 . 6 , 2. 2,

5.653

2

4.502) n ., d .

4 .. 1 1 8

q(7.7,

3 .. 9 8 6

q(7.7,

1 . 778)

3 ., 6 8 7

d(1.0,

4 . 502 )

1 . 937 )

CH CH(C)-13 3

1 0 .. 323 , 3 .628 , 1 0 .. 3 2 3 ,

3.564,

CH CH -8

1.937

2

3

1.778

CH CH -17

1 .963

CH -12

2

3

3

3, . 6 2 8

s

1 0 ,. 3 2 9

CH -18

3 . 590

s

1 0 ,. 3 2 9

CH -2

3 . 564

s

1 0 ,. 2 1 5

CH -7

1 0 ,. 2 1 5

CH -3

3 .556

s

**

in

5

1 0 . 329

5 ., 6 5 3

(as

C D N

6

3

3

3

3

d(7.1,

4 . 502)

n

.d.

CH^H-13

1 .937**

t(7.7,

4 . 118)

n

.d.

CH CH -8

1 .778

t(7.7,

3 . 986 )

n

.d.

CH CH -17

1 .963

*

3

when

Hz, S

partial

S coupled

signal

nuclei.

irradiated.

s a t u r a t i o n of

+

3

3

Chemical

§ Weak

shifts

enhancement

c l o s e meso-H. * *

Partially

where also

enhancements observed

overlapping

due

1

2

2

seen to

signals.


1

2.

CHICARELLI ET AL.

n


0.4


F i g u r e 4. U V / v i s i b l e (a) and EI probe mass (b) s p e c t r a l a

demetallated

chromatographic

fraction

isolated

crude o i l , and e n r i c h e d i n h i g h m o l e c u l a r weight

data f o r

from

Boscan

benzoporphyrins.


56

M E T A L C O M P L E X E S IN F O S S I L F U E L S

Origin

Considerations

It i s d i f f i c u l t having

the

since

no

to r a t i o n a l i s e

unusual known

this

dietary

study

feature, of

a

origin fused

25

i t s presence (45).

in

It

such

of

precursor

although

presence

being is

Serpiano

transformation the

f o r the a

of

the

On

shale

C-13"*"

that

reflects

the

fossil

methyl

other chlorin

metabolism

therefore,

also

in

(25),

the

i n a sponge o f a

a t t r i b u t e d to

pigments

component

moiety

feature.

possible,

oil

Serpiano

exocyclic ring

showed the o c c u r r e n c e

chlorophyll

presence

an

of

c h l o r o p h y l l contains

hand, a r e c e n t with

feature

of the

metabolic

water

column,

substituent

is

a


complicating factor. The

possibility

a l s o be

considered,

condensation

of

a

of

this

C-^

porphyrin

f o r i n s t a n c e , by compound

such

way

as

being

of

45,

an

an

artefact

unexpected

during

the

can

internal

treatment

with

methanesulphonic a c i d , a f t e r the F r i e d e l - C r a f t s a c e t y l a t i o n procedure employed f o r s e p a r a t i o n of components w i t h a /5H s u b s t i t u e n t from

co-

occurring

[as

the

solely

the

fully

copper(II)

alkylated species

complex] w i t h

deacetylated

counterpart

detect

compound

this

component w i t h

the

compound i s not total

porphyrins

the

after

(after

HPLC procedure s i m i l a r of

Such

sedimentary problems

a

that

vanadyl which

(23).

the

The

failure

prove t h a t

possibility

C-^

C^^

the

C-^

in

the

could

be

complex i n the

would

be

developed be

to

monoacetylated

porphyrins

might

45

unknown p o r p h y r i n

This

search

to

15

does not

by s e a r c h i n g f o r the vanadyl

metalloporphyrins.

any

of

demetallation).

of

acid afforded

base

a r t e f a c t formed from an

Serpiano

eliminate

free

treatment

u s i n g an separation

Treatment

methanesulphonic as

seven membered r i n g

an

e a s i l y excluded

(24,32).

total

facilitated

by

recently for (46),

and

associated

the

would

with

the

(12,13) s h a r e

with

demetallation procedure. The

two

demetallated

the d e m e t a l l a t e d of a methyl has

not

the

a precursor

Messel

with a

s u b s t i t u e n t at

been r e p o r t e d

c o u l d be

o i l shale

five

at C-15

Gilsonite

f u s e d r i n g Serpiano

porphyrins

component the s t r u c t u r a l

C-13*. As

i n any

i n d i c a t e d above, t h i s

biological

the

feature

t e t r a p y r r o l e pigment

f o r the sedimentary compounds. The of

feature

n i c k e l ( I I ) complex

of

a

which

discovery C-^

in

component

membered e x o c y c l i c r i n g c o n t a i n i n g a methyl s u b s t i t u e n t

l e d t o the s u g g e s t i o n

of an a c i d - c a t a l y s e d rearrangement o f

a d i a g e n e t i c product

of c h l o r o p h y l l c f o r the o r i g i n of the e x o c y c l i c

ring

this

(340 • B e a r i n g

Gilsonite

porphyrins

structures

such

represented

as f o l l o w s :

as

in

being the

mind,

one

formed

in

Gilsonite

could C^

an

perhaps

analogous compound

envisage way

which


to can

the give be

2.

C H I C A R E L L I ET A L .


Messel C-^ component The

G i l s o n i t e C-^ component

G i l s o n i t e component r e p r e s e n t e d

/J-ethyl s u b s t i t u e n t

i n any

c o n d e n s a t i o n r e a c t i o n proposed (34) i n the Messel component would not absence o f any o t h e r

component and because

i n t h i s way has,

i n a p o s i t i o n ( i . e . at C-2)

ethyl or vinyl substituent

the

57


the two

biological

however, a

not known t o have an

tetrapyrrole; also,

the

t o account f o r the e x o c y c l i c r i n g leave a C

information,

2

substituent

i t appears t h a t

a t C-13. I n the

Serpiano

G i l s o n i t e components may be r e l a t e d i n some way

o f t h e methyl

substituent

a t C-13

.

Indeed,

the

two

s t r u c t u r a l t y p e s c o u l d even have a common p r e c u r s o r : R

Precursor Tetrapyrrole

As

indicated

rearrangement

earlier,

i t i s difficult

o f a known c h l o r o p h y l l which

monobenzo[g]-porphyrins

23 and 24, a l t h o u g h

could

to give

propose rise

the p o s s i b i l i t y


to

a the

of a

58

M E T A L C O M P L E X E S IN FOSSIL FUELS

bacterial

origin

for

their

precursor

has

been

suggested

f u r t h e r c o m p l e x i t y i s added by the p r e l i m i n a r y e v i d e n c e a

pseudo-homologous

least

C}g>

series

i . e . components

of

such

with

components

several

S t r u c t u r a l s t u d i e s of the components > C-^ additional about

the

alkylation. origin

of

This the

may

provide

extending

additional

(36).

A

that there i s up

carbon

to

at

atoms.

s h o u l d r e v e a l the s i t e s of further information

monobenzo[g]porphyrins

or

either

about

the

d e g r a d a t i v e pathways g i v i n g r i s e to them.


Wider Geochemical C o n s i d e r a t i o n s Although i t i s d i f f i c u l t a t p r e s e n t to e n v i s a g e p l a u s i b l e o r i g i n s f o r some o f the sedimentary p o r p h y r i n s t r u c t u r e s now known, a knowledge of the s t r u c t u r e s of as many of the sedimentary components as p o s s i b l e s t i l l p r o v i d e s a more r e l i a b l e f o u n d a t i o n f o r comparative s t u d i e s of the o v e r a l l d i s t r i b u t i o n s i n d i f f e r e n t samples. For example, i t i s w e l l known from the d i s t r i b u t i o n s o b t a i n e d by HPLC t h a t the abundance of components w i t h an e x o c y c l i c a l k a n o ring relative to their aetioporphyrin counterparts decreases with i n c r e a s i n g e x t e n t of m a t u r a t i o n (47-50). T h i s concept i s r e a d i l y i l l u s t r a t e d i n F i g u r e 5, which shows the HPLC d i s t r i b u t i o n s of the demetallated porphyrins reported previously for four unrelated samples (21,23,50,51). Two o f the samples have been used e x t e n s i v e l y to p r o v i d e i n d i v i d u a l sedimentary p o r p h y r i n s f o r s t r u c t u r a l s t u d i e s ( T a b l e s I , I I ) : (a) G i l s o n i t e bitumen of Eocene age from the U i n t a B a s i n (USA); the d e p o s i t i o n a l environment of the source rock of t h i s sample i s thought t o have been l a c u s t r i n e and s t r o n g l y s a l i n e ( 5 2 ) . (b) Serpiano o i l shale, Triassic, from Monte San Giorgio, S w i t z e r l a n d , w i t h an e n c l o s e d marine d e p o s i t i o n a l environment. The o t h e r two samples a r e : (c) Guang-33 o i l , an immature o i l s h a l e of Eocene age from Jiangham s a l t l a k e b a s i n ( c e n t r a l - e a s t e r n C h i n a , Hubei P r o v i n c e ; 5 3 ) . (d) An immature sample of Kimmeridge c l a y of J u r a s s i c age from mainland U.K., from a s h a l l o w marine d e p o s i t i o n a l environment ( 5 0 ) . The p o r p h y r i n d i s t r i b u t i o n i n G i l s o n i t e bitumen i s more mature than the o t h e r t h r e e samples i n h a v i n g a h i g h e r abundance of a e t i o p o r p h y r i n s , which e l u t e w i t h r e t e n t i o n times l e s s than 32 minutes. Interestingly, the second most abundant component i n Gilsonite, the C-^ component w i t h the methyl substituted five membered e x o c y c l i c r i n g (12) has been c h a r a c t e r i s e d i n Guang33 o i l by comparison o f s p e c t r a l d a t a , and co-chromatography w i t h the component i s o l a t e d from G i l s o n i t e ( 5 1 ) , a l t h o u g h the s t r u c t u r e of the component was p r e v i o u s l y g i v e n i n c o r r e c t l y as 44 ( 4 3 ) . I t i s noteworthy t h a t i t



b)

30

30

(ENCLOSED MARINE)

SERPIANO SHALE:

20

(STRONGLY SALINE LACUSTRINE)

GILSONITE B I T U M E N :

JjJ

\ 40

A

40

OIL:

30

( S T R O N G L Y SALINE LACUSTRINE)

GUANG

T i m e (min)-

20

(SHALLOW

MARINE)

(j) KIMMERIDGE CLAY:

20

C)

30

12

40

Figure 5. High-performance liquid chromatograms of the total porphyrins (after demetallation) from four unrelated geological samples.

Q)

CL

a)



1: R " 2

= CH , R

8

2: R ' ' ' 1

3

5

2

= CH ,R ' ' '

= C H ^ ,R

9

= H

= CH , R ' '

6

= CH CH

9

= H or

4

6

3

3a: R ' ' ' ' 3b: R ' ' "

= CH ,R ' '

4

2

3c:

5

4

6

R " ' 2

7

5

8

4a: R " ' "

5

3

1

= CH , R

= CH CH , R

!

3

3

,

5

C H

5

'

,

9

CH CH , R

3

5

4

7

3

7

= CH , R '

6

CH , R

2

R

C H

.,2,5,7

R R

R

4,6

]

=

CH CH 2

1.2,4,7

3

3

4

R

=

CH ,

R

!

=

CH , 3

=

2

R '

5

R

6,8

R

6,8

R

6,8

3

- CH CH , ?

6,8

3

CH CH , 2

3

R

3

= CH CH , 2

3,5

3

1.3,4,7

CH CH , 2

3

=H

3

CH CH ?

=

3'

CH , R '

=H

3

2,4,6

2,4

=H

CH^CH,, R ~- H T " 3 ' 3,8 _ CH CH , R 2

= CH , R

, 3 , 5 , 7 __

8

3

3

1

8

3

6

2 , 8

2,4,6

CH,, R

2

= CH CH , R

3

1,3,5,7,

R '

3

- CH CH , R

3

1-3,5,7,

= CH CH ,

2

R '

y

3

2

4 , 6

6

4

3

D

- CH , R '

4

6,9

7 6 9 CH CH , R ^ ' ' =H ?

2

=H

9

3

2

4,7

CH , R '

H or

9

3

2

3

8

=H

9

3

CH CH , R

2,4,7

CH , R

1,5,7

13: R

I4d:

4,7

3

10: R ' ' '

14c:

2

3

CH , R

8

1,3,5,7

1

14b:

CH CH , R 2

R

1-3,5,7 9: R

14a:

6

= H or

9

3

7

2

3

7: R '

12: R

?

= H or

9

3

= CH CH , R

4 , 8

R

3 >

= CH CH , R ?

7

3

6: R ' ' '

11: R

6

2

= CH , R ' '

1,3,5,8 1

8: R

5

3

5

4b: R 1 - 3 . 5 . 6 , 8 5: R

3

3

7

3

3

1

8

1

3

3

3d: R ' " ' 1

1

= CH , R ' '

8

=H

7

2

8

9

3

8

2


= CH CH , R

1

3

3

= H or = H or = H cr -- H




CHICARELLI ET AL.




62




CHICARELLI ET AL.


64

M E T A L C O M P L E X E S IN F O S S I L F U E L S

does not o c c u r i n e i t h e r o f the two marine samples; i t s presence i n two samples from lacustrine, strongly saline depositional environments s u g g e s t s t h a t i t might be a s s o c i a t e d w i t h such a type o f environment. F u r t h e r s t u d i e s o f the p o r p h y r i n d i s t r i b u t i o n s from a wide variety of samples a r e n e c e s s a r y t o show whether these d i s t r i b u t i o n s c a n , i n d e e d , p r o v i d e i n f o r m a t i o n about d e p o s i t i o n a l environments. Conclusions 1.

The

number


emphasises in

of

sedimentary

porphyrin structures

now

elucidated

the remarkable c o m p l e x i t y o f the m i x t u r e s which can o c c u r

sediments

and

petroleums.

This

complexity

arises

from

the

v a r i a t i o n s which can o c c u r i n the d i a g e n e t i c r e a c t i o n s which a l t e r variety

of

precursors,

s t r u c t u r e s of s e v e r a l

mainly

of the compounds cannot

r e l a t e d t o known b i o l o g i c a l 2.

The

determination

correcting has

only

chlorophylls.

addition,

a t p r e s e n t be

a

the easily

pigments.

of

three

novel

a p r e v i o u s misassignment been found

In

to date

structures

f o r one

is

described,

o f them. T h i s component

i n high r e l a t i v e

abundance

in

samples

from l a c u s t r i n e , s t r o n g l y s a l i n e , d e p o s i t i o n a l environments. 3.

Although p o s s i b l e

clear,

a

knowledge

comparison

of

the

origins of

o f many o f the compounds a r e not

their

structures

distributions

obtained

yet

provides

more

effective

by

from

different

HPLC

sediments and p e t r o l e u m s . 4. In o r d e r t o u n d e r s t a n d the o r i g i n s of the more unusual s e d i m e n t a r y components and

the d e g r a d a t i v e pathways l e a d i n g

t o them,

structural

e l u c i d a t i o n work s i m i l a r t o t h a t d e s c r i b e d and reviewed h e r e i n s h o u l d be

applied

samples

and

to

components

from

those examined

older

isolated

samples

with

from

contemporary

a milder

sedimentary

thermal h i s t o r y

than

t o date ( T a b l e I , I I ) .

Acknowledgments We a r e g r a t e f u l t o the B r i t i s h P e t r o l e u m p i c and the N a t u r a l Environment Research C o u n c i l (GR3/2951 and GR3/3758) f o r p r o v i d i n g HPLC and MS f a c i l i t i e s , r e s p e c t i v e l y . Two o f us thank the B r a z i l i a n N a t i o n a l Research C o u n c i l , CNPq (M.I.C.) and the N a t u r a l Environment Research C o u n c i l (S.K.) r e s p e c t i v e l y f o r Research S t u d e n t s h i p s . D r s . M. Murray (University of B r i s t o l ) , 0. Howarth and E. Curzon ( U n i v e r s i t y of Warwick) a r e g r a t e f u l l y acknowledged f o r r u n n i n g NMR s p e c t r a and Dr. T. Peakman f o r v a l u a b l e d i s c u s s i o n s . Dr. K.A.G.


2.

C H I C A R E L L I ET AL.


65

MacNeil ( U n i v e r s i t y o f B r i s t o l ) i s thanked f o r HRMS a n a l y s e s , and R. Pitt f o r assistance with the i s o l a t i o n o f t h e two G i l s o n i t e porphyrins.

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