Electrochemistry of nitrite reductase model compounds .6. Voltammetric and spectroelectrochemical studies of iron(II) nitrosyl complexes with porphyrins, hydroporphyrins and porphinones

被引:29
作者
Liu, YM [1 ]
DeSilva, C [1 ]
Ryan, MD [1 ]
机构
[1] MARQUETTE UNIV,DEPT CHEM,MILWAUKEE,WI 53201
关键词
electrochemistry; spectroelectrochemistry; iron complexes; porphyrin complexes; nitrosyl complexes;
D O I
10.1016/S0020-1693(96)05547-8
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
The effect of hydroporphine and porphinone macrocycles on the voltammetry and spectroscopy of Fe(P)(NO) was examined. Two oxidation and two reduction waves were observed for all the complexes examined. The variation in the half-wave potentials fell into two categories: those where the E-1/2 of the complex varied linearly with the E-1/2 of the free-base, and those where the relationship was non-linear. Linear relationships were observed where the electron transfer was primarily macrocycle-centered, while non-linear relationships were observed for metal-centered processes. Of the four waves observed, the first reduction and second oxidation of Fe(P) (NO) was non-linear, while the second reduction and first oxidation waves were linear. Comparison with the voltammetry of Fe(P) (Cl) showed the same relationships. The first reduction and second oxidation waves were non-linear while the second and third reductions and the first oxidation waves were linear. For the linear relationships, where the E-1/2 Of the complex wats proportional to the E-1/2 Of the free-base, the energy of the LUMO or HOMO controlled the redox potential so that the porphyrin molecular orbital was involved substantially in the redox product, if not itself oxidized or reduced. This would indicate that the first reduction of Fe(P)(NO) was centred on the Fe(NO) moiety, while the second reduction led to the formation of a porphyrin radical anion. The variation in oxidation redox potentials was consistent with previous formulations of Fe(P) (NO)(+) as a pi-cation radical (except for Fe(OEP) (NO)(+)). The variations in the E-1/2 of the second oxidation wave would indicate that the oxidation was centred on the Fe(NO) moiety. The variation in the half-wave potentials of Fe(X-TPP)(NO), where X was a substituent at the three- or four-position on the phenyl ring, also confirmed this interpretation. The slope of the E-1/2 values for the first wave was 0.045 V, while a value of 0.072 V was observed for the second wave. It has been previously shown that slopes of about 0.068 V were indicative of porphyrin reduction, while lower values were generally observed for metal reduction. The formation constants for pyridine with Fe(P) (NO) were also determined. For the porphyrins and hydroporphyrins, the values were small (about 0.3 to 1.1),which were consistent with other iron nitrosyl porphyrins and chlorins. The porphinone and porphinedione complexes, though, showed a much greater affinity for pyridine, with formation constants of 4.8 +/- 0.2 and 88 +/- 3. These values are one to two orders of magnitude larger than the values observed for other iron-porphyrin nitrosyl complexes, and indicate a chemical advantage for the porphinedione (heme d(1)) in dissimilatory nitrite reductases, where the heme is coordinated by an imidazole in the fifth position. A weak complex (K=9) was observed between Fe(2,4-OEiBC) (NO)(+) and pyridine.
引用
收藏
页码:247 / 255
页数:9
相关论文
共 48 条
[1]   ON PREPARATION OF METALLOPORPHYRINS [J].
ADLER, AD ;
LONGO, FR ;
KAMPAS, F ;
KIM, J .
JOURNAL OF INORGANIC & NUCLEAR CHEMISTRY, 1970, 32 (07) :2443-&
[2]   A SIMPLIFIED SYNTHESIS FOR MESO-TETRAPHENYLPORPHIN [J].
ADLER, AD ;
LONGO, FR ;
FINARELLI, JD ;
GOLDMACH.J ;
ASSOUR, J ;
KORSAKOF.L .
JOURNAL OF ORGANIC CHEMISTRY, 1967, 32 (02) :476-+
[3]   MODELS OF HEME-D1 - MOLECULAR-STRUCTURE AND NMR CHARACTERIZATION OF AN IRON(III) DIOXOISOBACTERIOCHLORIN (PORPHYRINDIONE) [J].
BARKIGIA, KM ;
CHANG, CK ;
FAJER, J ;
RENNER, MW .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1992, 114 (05) :1701-1707
[4]   C-HYDROXYCHLORINS AND C-METHYLCHLORINS - A CONVENIENT ROUTE TO HEME-D AND BONELLIN MODEL COMPOUNDS [J].
CHANG, CK ;
SOTIRIOU, C .
JOURNAL OF ORGANIC CHEMISTRY, 1985, 50 (24) :4989-4991
[6]   MODELS OF SIROHEME AND SIROHYDROCHLORIN - PI-CATION RADICALS OF IRON(II) ISOBACTERIOCHLORIN [J].
CHANG, CK ;
FAJER, J .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1980, 102 (02) :848-851
[7]   DIFFERENTIATION OF BACTERIOCHLORIN AND ISOBACTERIOCHLORIN FORMATION BY METALATION - HIGH-YIELD SYNTHESIS OF PORPHYRINDIONES VIA OSO4 OXIDATION [J].
CHANG, CK ;
SOTIRIOU, C ;
WU, W .
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, 1986, (15) :1213-1215
[8]   MODELS OF HEME-D1 - STRUCTURE AND REDOX CHEMISTRY OF DIOXOISOBACTERIOCHLORINS [J].
CHANG, CK ;
BARKIGIA, KM ;
HANSON, LK ;
FAJER, J .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1986, 108 (06) :1352-1354
[9]   ELECTROCHEMICAL AND SPECTROSCOPIC STUDIES OF IRON PORPHYRIN NITROSYLS AND THEIR REDUCTION PRODUCTS [J].
CHOI, IK ;
LIU, YM ;
FENG, D ;
PAENG, KJ ;
RYAN, MD .
INORGANIC CHEMISTRY, 1991, 30 (08) :1832-1839
[10]  
CHOI IK, IN PRESS INORG CHEM