Isocyanide or nitrosyl complexation to hemes with varying tethered axial base ligand donors: synthesis and characterization
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A series of ferrous-heme 2,6-dimethylphenyl isocyanide (DIMPI) and ferrous-heme mononitrosyl complexes have been synthesized and characterized. The heme portion of the complexes studied is varied with respect to the nature of the axial ligand, including complexes, where it is covalently tethered to the porphyrinate periphery. Reduced heme complexes, [(F8)FeII], [(PPy)FeII], [(PIm)FeII], and [(PImH)FeII], where F8 = tetrakis(2,6-difluorophenyl)-porphyrinate and PPy, PIm, and PImH are partially fluorinated tetraaryl porphyrinates with covalently appended axial base pyridyl/imidazolyl or histamine moieties, were employed; PImH is a new construct. Room temperature addition of DIMPI to these iron(II) complexes affords the bis-isocyanide species [(F8)FeII-(DIMPI)2] in the case of [(F8)FeII], while for the other hemes, mono-DIMPI compounds are obtained, [(PPy)FeII-(DIMPI)] [(2)-DIMPI], [(PIm)FeII-(DIMPI)] [(3)-DIMPI], and [(PImH)FeII-(DIMPI)] [(4)-DIMPI]. The structures of complexes (3)-DIMPI and (4)-DIMPI have been determined by single crystal X-ray crystallography, where interesting H…F(porphryinate aryl group) interactions are observed. 19F-NMR spectra determined for these complexes suggest that H…F(porphyrinate aryl groups) attractions also occur in solution, the H atom coming either from the DIMPI methyl groups or from a porphyinate axial base imidazole or porphyrinate pyrrole. Similarly, we have used nitrogen monoxide to generate ferrous-nitrosyl complexes, a five-coordinate species for F8, [(F8)FeII-(NO)], or low-spin six-coordinate compounds [(PPy)FeII-(NO)], [(PIm)FeII-(NO)], and [(PImH)FeII-(NO)]. The DIMPI and mononitrosyl complexes have also been characterized using UV–Vis, IR, 1H-NMR, and EPR spectroscopies.
KeywordsFerrous heme Heme isocyanide X-ray structures Heme nitrosyl H…F(porphyrinate) interactions
This work was supported by the National Institutes of Health (R01 GM 060353 to K.D.K).
- 1.Ghosh A (ed) (2008) The smallest biomolecules: diatomics and their interactions with heme proteins. Elsevier, AmsterdamGoogle Scholar
- 3.Aono S (2008) Dalton Trans 3137–3146Google Scholar
- 5.De Montellano PRO (2005) Cytochrome P-450: structure, mechanism, and biochemistry. SpringerGoogle Scholar
- 9.Ford PC, Bandyopadhyay S, Lim MD, Lorkovic IM (2008) The smallest biomolecules: diatomics and their interactions with heme proteins. In: Ghosh A (ed) Elsevier, Amsterdam, pp 66–91Google Scholar
- 50.Song B, Yu B-S (2003) Bull Korean Chem Soc 24:981–985Google Scholar
- 52.A reviewer suggested the bending may be due to a pseudo Jahn-Teller effect arising from a slight weakening of the Fe-N5(imidazole) bond in (3)-DIMPI compared to that in (4)-DIMPI (see Table 2); see Kitagawa T et al. (2005) J Phys Chem B 109: 21110-21117Google Scholar
- 59.As suggested by a reviewer, the room-temperature molecular structures for (3)-DIMPI and (4)-DIMPI may be dynamic with respect to Fe-C-N bending; the IR band observed for these complexes do seem to be asymmetric, and composed of two bands, possibly two conformersGoogle Scholar
- 60.Lehnert N, Scheidt WR, Wolf MW (2014) In: Mingos DMP (ed) Nitrosyl complexes in inorganic chemistry, biochemistry and medicine ii. Springer, New York, pp 155–223Google Scholar