TPP structure

Complexes of tetrapheny I porphyrin (TPP, R, Rs H, R = C6H5) have been studied most extensively due to their relatively high-yield synthesis and convenient purification. Thus, many biomimetic compounds such as picket-fence and capped porphyrins (Sec. V-l) have been derived from the basic TPP structure. However, IR spectra of TPP complexes are extremely difficult to assign because vibrations of phenyl groups are mixed with or overlapped by those of the porphyrin-core. Recently, Oshto et al. " prepared 20 Fe(TPP)LL - (L, L axial ligands) type complexes, and located two spin-state... 

For comparison purposes, selectivity data is also presented for membranes prepared with a typical quaternary ammonium exchanger, tridodecylmethylammonium chloride (TDMA-Cl) (1). All the porphyrin species tested yield selectivities which clearly deviate from that observed with TDMA-Cl. More importantly, two compounds, Mn[TPPP]Cl (i) and Sn[TPP]Cl2 (5.), show extraordinary selectivity toward thiocyanate and salicylate, respectively. In the case of Mn[TPPP]Cl, adding conjugated and bul)cy substituents in the form of twelve phenyl groups to the basic tetraphenylporphyrin [TPP] structure dramatically enhances the response and selectivity toward thiocyanate... 

Therefore, 14 could be an analog of a-lactyl-TPP. An analog of a reactive intermediate in an enzymic reaction should bind tighdy with the enzyme. The crystal structure of 14 was further reported by Turano et al. [59]. Furey and Jordan have also confirmed a similar phosphonolactyl-TPP structure by a high resolution crystal structure and spectroscopic analysis. It was observed that this type of compound was bound in the pyruvate dehydrogenase El-subunit [60, 61]. 

Figure 1 shows the chemical structure ofvitamin B1 or thiamin (3-(4-amino-2-methyl-pyrimidin-5-ylmethyl)-5-(2-hydroxyethyl)-4-methylthiazolium) and its coenzyme form thiaminpyrophosphate (TPP). 

Vitamin B1. Figure 1 Structure of thiamin and its coenzyme form thiaminpyrophosphate (TPP). 

The tendency to form ate complexes observed for yttrium is also seen in the preparation of a novel zirconium alkynyl complex. Reaction of Zr(Por)Cl2 (Por = OEP or TPP) with either two or three equivalents of LiC=CR (R = Ph or SiMe ) gives the trisalkynyl complexes Zr(Por)(C=CR)3Li(TFIF). An X-ray crystal structure of Zr(OEP)(C=CPh)2Li(THF) shows that all three alkynyl ligands are on... 

The electronic absorption spectra of the products of one-electron electrochemical reduction of the iron(III) phenyl porphyrin complexes have characteristics of both iron(II) porphyrin and iron(III) porphyrin radical anion species, and an electronic structure involving both re.sonance forms Fe"(Por)Ph] and tFe "(Por—)Ph has been propo.sed. Chemical reduction of Fe(TPP)R to the iron(II) anion Fe(TPP)R) (R = Et or /7-Pr) was achieved using Li BHEt3 or K(BH(i-Bu)3 as the reductant in benzene/THF solution at room temperature in the dark. The resonances of the -propyl group in the F NMR spectrum of Fe(TPP)(rt-Pr) appear in the upfield positions (—0.5 to —6.0 ppm) expected for a diamagnetic porphyrin complex. This contrasts with the paramagnetic, 5 = 2 spin state observed... 

Insertion of SO2 into the Fe—C bond in FelPorfCHi was first reported in 1982, giving the sulfinato complexes Fe(Por)S02CH2, which are moderately air stable but can be further oxidized by O2 to give the sulfonato complexes FelPorfSOiCH. " Alkyliron(Ill) porphyrins insert CO to give the acyl complexes Fe(Por)C(0)R. For example, Fe(TPP)C(0)-n-Bu was formed either by this method or by the reaction of I Fe(TPP) r with ClC(0)-/ -Bu, and was characterized by an X-ray crystal structure... 

Dihalocarbene complexes are useful precursors to new carbenes by nucleophilic displacement of the chlorine substituents. This has been nicely illustrated for Fe(TPP)(=CCl2) by its reaction with two equivalents of Re(CO)5J to give the unusual /t-carbido complex Fe(TPP)=C=Re(CO)4Re(CO)5 which also contains a rhenium-rhenium bond. " The carbido carbon resonance was observed at 211.7 ppm in the C NMR spectrum. An X-ray crystal structure showed a very short Fe=C bond (1.605(13) A, shorter than comparable carbyne complexes) and a relatively long Re=C bond (1.957( 12) A) (Fig. 4, Table III). " ... 

Several examples of carbene complexes have been structurally characterized (Fig. 5), and selected data for Ru(TPP)(=C(C02Et)2)(Me0H). Os(TTP)-(=C(p-C(,H4Me)2)(THF), Os(TTP)(=CHSiMe2)(THF), Os(TTP)(=SiEt2THF)-(THF) and a /x-carbido phthalocyanine complex, Ru(Pc)(py)]2C, are given in Table The ruthenium carbene complex has a Ru=C bond signifi-... 

Fig. 1 Ball and stick drawings of the structures of (a) [Fe(F2o-TPP)(CPh2)] 0.5C6H6 0.5CH2Cl2 and (b) [Fe(F2o-TPP)(CPh2)(MeIni)]. The solvent molecules and/or hydrogen atoms are not shown [22]...

Fe(TPP)(CCl2)(H20)] is not significantly displaced from the porphyrin plane. Despite the different structures of [Fe(F20-TPP)CPh2], [(Melm)Fe(F2o-TPP) CPh2], and [Fe(TPP)(CCl2)(H20)], the average Fe-N(pyrrole) distances in these three complexes are similar. 

More recently 233) it has been reported that cross-linked polystyrene containing imidazole ligands did not provide a support rigid enough to prevent dimerization, and that the p-oxo dimer was benzene extracted from oxygenated tetraphenyl porphyrin iron(ll), Fe(TPP), which had been attached to the modified polystyrene. A discussion of model synthetic porphyrins, from which definitive structural and other physical data are obtained, is given in section V.C. 

The current example illustrates PVDOS formulation as an effective basis for comparison of experimental and theoretical NIS data for ferrous nitrosyl tetraphe-nylporph3Tin Fe(TPP)(NO), which was done [101] along with other ferrous nitrosyl porphyrins. Such compounds are designed to model heme protein active sites. In particular, the elucidation of the vibrational dynamics of the Fe atom provides a unique opportunity to specifically probe the contribution of Fe to the reaction dynamics. The geometrical structure of Fe(TPP)(NO) is shown in Fig. 5.16. 

Fig. 5.16 Calculated structure of ferrous nitrosyl tetraphenylporphyrin Fe(TPP)(NO), resulting from geometric optimization with the B3LYP functional and 6-3IG -I- VTZ basis set [101]. Color scheme cyan = iron, green = carbon, blue = nitrogen, red = oxygen (taken from [101])...

THF solution [290]. There had been much confusion in the past about the magnetic moment of the iron(I) species and the correct Mossbauer and NMR properties caused by impurities of the samples and possible unknown axial ligation. However, with clean crystallized samples with known molecular structure [291], the first reduction product of iron(II)(tetraphenylporyphrin), [Fe(TPP)], can be clearly characterized as a quasiplanar iron(I) complex with spin S = 1/2 (EPR = 2.28,... 

The Mossbauer spectrum of the dianion was a surprise because the isomer shift (5 = 0.48 mm s ) was substantially more negative than that of the monoanion, and resembles more that of Fe(II)(TPP) than that of [Fe(I)TPP] . Reed and Scheldt therefore suggested a resonance hybrid of iron(I) and iron(II) for the electronic structure of the dianion molecule instead of the formulation [Fe(0)(TPP)] [290, 291]. 

---