Unexpected tetracoordinated iron(II) bis-strapped chiral porphyrin bearing a nitrogen base on one handle

Tetrahedron Letters,Vol.29,No.44,pp Printed in Great Britain

5653-5656,1988

UNEXPECTED TETRACOORDINATED

IRON

0040-4039/88 $3.00 + .OO Pergamon Press plc

BIS-STRAPPED CHIRAL

PORPHYRIN BEARING A NITROGEN BASE ON ONE HANDLE

Bernard

BOITREL,

Alexandra

Universiti? P. et M. Curie, Laboratoire

de Chimie

Tour 45, 4 Place Jussieu

Syntheses

of chiral

porphyrins'

for example

by two chiral

straps

- firstly to understand

for unconstrained

for example

to cytochrome

some properties

P-450 or as models if they are

:

in order

configuration

why the CO ligand exhibits

plane

of the strap

in asymmetric

we devoted

rigidity

tetracoordinated

iron

res-

is not observed

in refluxing

that internal

of a detailed

shifted

crystal

of a

site and to

5653

a square of CHC13

to the protons

pyridines

of

do not coor-

we cannot be sure of

of the porphyrin

compound,

to coordinate

yields

or a mixture

shielding

structure

from the doming7

in order

toluene

pyridine

and external

that the five-coordinated ligand

base near the active

in MeOH,

(large contact

but it can derive

the pyridine

nitrogen

to the preparation

ligands.

is only soluble

interesting

this means

now our results

and 2,6-lutidine

is paramagnetic6

of this effect,

towards

to synthesize chiral hindered porphyrins, lb,c,e porphyrins (la) in order to study the

an axial

external

In the absence

In other words,

of the plane

FeClz4

(lb) which

It is especially

the iron atom.

bearing

towards

of (la) with

This compound

the straps).

this ligand geometry

with

efforts

and "his-strapped"

iron-porphyrin

complex

considerable

of the straps. We extend

of its properties

Metallation

a bent or titled configuration

in the case of Hb' because

"gyroscope-like"

conformational

the origin

in order to mimic

related

heme derivatives3.

For this reason,

strap.

au CNRS 408

bearing a pyridine handle yields due to the conformational

could be of great importance

the role of the molecular

to understand

pect to the porphyrin

and MeOH.

Unite Associee

;

rynthesis

- secondly

the study

catalyts

(Hb). They

*

75252 PARIS Cedex 05, France

have been investigated

as oxydation

to oxy and carbonyl-hemoglobin

protected

dinate

Organique,

of iron into a bis-strapped porphyrin an unexpected tetracoordinated iron(porphyrin rigidity of the straps.

of hemoproteins,

planar

and ERIC ROSE

: Insertion

Abstract .~___

related

LECAS

bringing

it, cannot

by the other the iron out 6

be formed

.

5654

Bubbling

CO into a pyridine

a six-coordinated strap is capable porphyrin

diamagnetic

iron

of coordinating

ring3b.

(2b), which

or CHc13/~ MeOH solution

Metallation

implies

again,

derivative

(Id). This indicates

in this case , where

of (Za) yields

that a second

of the iron(I1)

iron is probably

an hexacoordinated

porphyrin

that the pyridine in the plane of the

diamagnetic

ligand causes the pyridine

(lb) gave

metalloporphyrin

strap to coordinate.

The

2OOMHz 'H NMR spectrum of (lb) in CD30D shows peaks between +17 and -78ppm, typical of an lf,5d iron porphyrin . The 'H NMR "2D-COSY" spectrum shows clearly the correlation of the peaks of the alanine

residues

and of 14 meso-phenyl

protons.

-77.92 and -42.36 ppm reveal the very short separation protons

from the iron atom which

(lb). The 'H NMR "2D-COSY" resonance complete

at 7.50 (para-PyH) agreement

In conclusion, results

show

rigidity

is correlated

to the resonance

of the metalloporphyrin

porphyrin

(Id) shows that the

at 2.50 ppm (ortho-PyH)

in

of the pyridine handle to the metal iron6 (table 1). 8 et al. , the terephtalic strap should lay about 3.1:

knowing

that the porphyrins

that the pyridine

nitrogen

nitrogen

it. This represents

(If) and (lb) differ only by two carbons,

of the ansa-compound

of the same handle to our knowledge

and the CNRS for financial

Table

(la)

ansa-compound

our

the metal,

chiral handles.

Drs C.Knobler

and M.Momenteau

and N.Morin

for helpful

dis-

for mass spectra*, Rhcne-

support.

1

: Selected

a,g,e(lb)c,d

(ld)bsd'f

3.74"

5.36

(2a)ayd

(2c)aSd'

6.11

-9.001

6.64

1.68

1.33

6.51

1.99

1.53

J!-PY

4.56

-77.923

4.71

6.74

6.68

4.77

6.91

6.59

(d) 2OOMHz N.M.R

--

(2b)a'd'h

o-PY

(c) CD30D

5.77

(le)bSd

4.17"

(b) CDC13/s CD30D

-42.36

(lc)a,d,m,

1 H NMR data (6 ppm)

I?-CgH4-

(a) CDC13

but

(lb) does not

the first example of such a conformational

for a gift of 13C0, Drs M.Rolando

M.Momenteau

(If) coordinates

of the shorter

hooked by two different

We thank Profs. .J.P.Collman, J.Levisalles,

Poulenc

rigidity

iron(I1)

at

and terephtalic

model of Abraham

of an iron porphyrin

cussions,

resonances

plane.

that the same pyridine coordinate

of the diamagnetic

with coordination

Using the ring current from the porphyrin

shows the conformational

spectrum

Two high-field

of the para-pyridinic

(e) 5OOMHz N.M.R

--

--

(f) 13C N.M.R

:

Fe-13CO=199.4 (CDC13/&CD30D) : this unusual high field value compared with carbonyl6a,9b 9a will be discussed elsewhere (g) 4OOMHz N.M.R (h) R'CH3 and models values hemoglobin (i) R=CH2Ph

(j) meso-phenyl

protons

: 17.08 (2H) k , 13.79 (2H), 12.42 (6H), 11.38 (2H),

11.14 (2H), 9.32 (2H) (k) we do not see the correlation be a 2H ArH resonance (2H) which protons5d

(1) the four peaks at 26.52

are not observed

in CD30D were attributed

and to the 4 NH protons

of the aminoacid.

of this peak, so we postulated

(2H). 22.10

(2H), and -9.95

respectively The alanine

it to

(2H), -13.90

to the 4 NH meso-phenyl peaks were attributed

at

5656

2.32 , 2.00

and -1.29, -0.69 and the 8 pyrrolic peaks at 8.66, 8.46, 8.13, 7.82 (m) (lc)

is prepared like (la) using p-phenylenediaceticchloride instead of terephtaloic chloridele,j (n) The shielding ot the terephtalate protons of (la) is 4.09 ppm relative to the chemical shifts of the terephtaloic chloride. This is 3.55 ppm in the case of (le).

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All compounds described have been fully characterized spectroscopically(UV-vis, NMR) and by accurate mass determination and/or elemental analysis. (Received

in France

10 May 1988)