research papers
(
2
Gangopadhyay et al., 1994; Tollari et al., 1996; Yuan et al.,
010; Zhou et al., 2012). This reactivity is particularly
porphyrin)manganese(III)–1,4-diazabicyclo[2.2.2]octane–tolu-
ene–water (4/4/4/1), [Mn(TPP)Cl(DABCO)]ꢀ(DABCO)ꢀ-
appealing for incorporation in solid-state materials, such as
thin-film-deposited surfaces (Hod et al., 2015; Betard &
Fischer, 2012), zeolites (Kadish et al., 2003), or metal–organic
frameworks (MOFs) (Feng et al., 2012).
(toluene)ꢀ0.25H O, (IV), as well as a fourth complex,
2
chlorido(pyridine)(5,10,15,20-tetraphenylporphryinato)man-
ganese(III) pyridine disolvate, [Mn(TPP)Cl(py)]ꢀ2(py), (III),
a structure previously published by Kirner & Scheidt (1975),
but prepared by a new method of crystallization and having a
slightly different structure than that reported previously
(Scheme 1). The series of amines, i.e. imidazole, piperidine,
pyridine, and DABCO, present a range of basicities and axial
coordination affinities. Piperidine, based on literature prece-
dents (Berezin, 1980), can cause the reduction of the Mn
II
porphyrin complex, leading to the formation of a Mn
porphyrin species. Axial ligand binding constants for two of
the complexes were determined in chloroform solution and
are reported and discussed.
2
. Experimental
2.1. Synthesis and crystallization
TPP, Mn(TPP)Cl, [Mn(TPP)(im) ]Clꢀ2CHCl , [Mn(TPP)-
2
3
(
pip) ]Cl, [Mn(TPP)Cl(py)]ꢀ2(py), and [Mn(TPP)Cl(DAB-
2
CO)]ꢀ(DABCO)ꢀ(toluene)ꢀ0.25H O were synthesized accor-
2
ding to the methods described below. All other reagents were
purchased commercially and used without further purification.
2.1.1. Synthesis of 5,10,15,20-tetraphenylporphyrin (TPP).
TPP was made following the literature procedure of Adler et
al. (1966). Pyrrole (5.6 ml, 80 mmol) was added to boiling
propionic acid. Benzaldehyde (8 ml, 78 mmol) was then added
to the reaction mixture. The reaction continued for 40 min and
was then allowed to cool to room temperature. Violet crystals
were collected by filtration, washed with methanol and water,
and dried in a vacuum oven for 2 h (yield 20%).
The key to their biological function and catalytic behavior
in protein or other environments lies in their affinity for axial
binding at the metalloporphyrin active sites. In-depth char-
acterization of these metalloporphyrin complexes with a range
of axially coordinating ligands therefore continues to be an
important avenue of investigation for understanding their
reactivity in these environments (Kadish et al., 1999b;
Meunier, 1992; Hanson, 1979). Amine-based axial ligands are
important for their biological and catalytic relevance. While
the structures and axial ligation properties of iron porphyrin
complexes with several nitrogenous base ligands have been
thoroughly explored (Castro, 1974; Collman, 1980; Ricard et
al., 2001; Ma et al., 2013), their manganese counterparts have
undergone far less characterization (Calvin, 1965; Boucher,
2.1.2. Synthesis of (5,10,15,20-tetraphenylporphyrinato)-
manganese(III) chloride, Mn(TPP)Cl. This precursor was
prepared according to the literature procedure of Feng et al.
(2012). TPP (1.0 g, 1.6 mmol) was dissolved in DMF and
MnCl (3.0 g, 24 mmol) was added. The reaction was refluxed
2
overnight, then stopped and allowed to cool to room
temperature. Water was added to the reaction mixture and a
green powder was filtered off. The resulting powder was
dissolved in chloroform and washed with 1 M HCl solution
(ꢁ3) and water (ꢁ2). The resulting organic layer was dried
over anhydrous sodium sulfate for 1 h (yield 68%).
1972; Day et al., 1974; Gonzalez et al., 1975; Kirner & Scheidt,
1975). Moreover, the planarity of the porphyrin ring and its
relation to the binding affinities of the ligand is an important
aspect of metalloporphyrin chemistry that has been exten-
sively studied for nickel (Jia et al., 1998; Duval et al., 1999;
Song et al., 2005) and iron porphyrin complexes (Lever &
Gray, 1983), but not for the manganese porphyrin analogues.
In this article, we present the syntheses and crystal and mol-
ecular structures of three new manganese porphyrin
complexes with different nitrogenous base ligands, namely
bis(imidazole)(5,10,15,20-tetraphenylporphyrinato)mangan-
ese(III) chloride chloroform disolvate, [Mn(TPP)(im)2]-
2.1.3. Synthesis of bis(imidazole)(5,10,15,20-tetraphenyl-
porphyrinato)manganese(III) chloride chloroform disolvate,
[Mn(TPP)(im) ]Clꢀ2CHCl , (I). Complex (I) was synthesized
2
3
according to a modified literature procedure for the prepar-
ation of a similar iron(III) complex, i.e. [Fe(TPP)(HIim) ]Cl
2
(Scheidt et al., 1987). Mn(TPP)Cl (50 mg, 0.071 mmol) was
mixed with imidazole (20 mg, 0.30 mmol) in chloroform (4 ml)
in a 20 ml scintillation vial. A 2:1 (v/v) hexane–chloroform
solution was added (15 ml), utilizing the layering technique, to
the Mn(TPP)Cl-imidazole mixture. The resulting mixture was
left to infuse and crystallize for a minimum of 3 d. The
resulting dark-green crystals were filtered off and washed with
hexanes (yield 95%).
Clꢀ2CHCl , (I), bis(piperidine)(5,10,15,20-tetraphenylporphy-
3
rinato)manganese(III) chloride, [Mn(TPP)(pip) ]Cl, (II), and
2
chlorido(1,4-diazabicyclo[2.2.2]octane)(5,10,15,20-tetraphenyl-
ꢂ
Acta Cryst. (2019). C75, 304–312
Lahanas et al.
Manganese porphyrin complexes with nitrogenous bases 305
Lahanas, Nicole
