313391-45-6

Upstream product

• 109-99-9 tetrahydrofuran 
• 953387-00-3 (chloro)(2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetrphenylporphyrinato)iron(III) complex 

Downstream Products

• 362651-54-5 [Fe(5,10,15,20-tetraphenyl-2,3,7,8,12,13,17,18-octaethylporphyrin)(imidazole)2]ClO₄ 
• 353750-00-2 bis(tert-butylisocyanide)[(2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrinato)iron(III)] perchlorate 
• 953386-86-2 [(octaethyltetraphenylporphyrinato)Fe(tert-butylisocyanide)2]Cl 

Relevant academic research and scientific papers

Formation of pure intermediate spin complexes in highly nonplanar iron(III) porphyrins

Bis(thf)(porphyrinato)iron(III) complexes with highly S4-ruffled and S4-saddled porphyrin cores are determined to be very pure intermediate spin complexes on the basis of NMR, EPR, Mossbauer, and magnetic data.

Metal-porphyrin orbital interactions in highly saddled low-spin iron(iii) porphyrin complexes

Substituent effects of the meso-aryl (Ar) groups on the 1H and 13C NMR chemical shifts in a series of low-spin highly saddled iron(III) octaethyltetraarylporphyrinates, [Fe(OETArP)L2] +, where axial ligands (L) are imidazole (Hlm) and tert-butylisocyanide (tBuNC), have been examined to reveal the nature of the interactions between metal and porphyrin orbitale. As for the bis(Hlm) complexes, the crystal and molecular structures have been determined by X-ray crystallography. These complexes have shown a nearly pure saddled structure in the crystal, which is further confirmed by the normal-coordinate structural decomposition method. The substituent effects on the CH2 proton as well as meso and CH2 carbon shifts are fairly small in the bis(Hlm) complexes. Since these complexes adopt the (dxy)2(d xz, dyz)3 ground state as revealed by the electron paramagnetic resonance (EPR) spectra, the unpaired electron in one of the metal dπ orbitals is delocalized to the porphyrin ring by the interactions with the porphyrin 3eg-like orbitale. A fairly small substituent effect is understandable because the 3eg-like orbitale have zero coefficients at the meso-carbon atoms. In contrast, a sizable substituent effect is observed when the axial Hlm is replaced by tBuNC. The Hammett plots exhibit a large negative slope, -220 ppm, for the meso-carbon signals as compared with the corresponding value, +5.4 ppm, in the bis(Hlm) complexes. Since the bis(tBuNC) complexes adopt the (dxz, dyz)4(dxy)1 ground state as revealed by the EPR spectra, the result strongly indicates that the half-filled dxy orbital interacts with the specific porphyrin orbitale that have large coefficients on the meso-carbon atoms. Thus, we have concluded that the major metal-porphyrin orbital interaction in low-spin saddle-shaped complexes with the (dxz, dyz) 4(dxy)1 ground state should take place between the d xy and a2u-like orbital rather than between the d xy and a1u-like orbital, though the latter interaction is symmetry-allowed in saddled D2d complexes. Fairly weak spin delocalization to the meso-carbon atoms in the complexes with electron-withdrawing groups is then ascribed to the decrease in spin population in the dxy orbital due to a smaller energy gap between the d xy and dπ orbitale. In fact, the energy levels of the dxy and dπ orbitals are completely reversed in the complex carrying a strongly electron-withdrawing substituent, the 3,5-bis(trifluoromethyl)phenyl group, which results in the formation of the low-spin complex with an unprecedented (dxy)2(d xz, dyz)3 ground state despite the coordination of tBuNC.

Electronic structures of six-coordinate ferric porphyrin complexes with weak axial ligands: Usefulness of 13C NMR chemical shifts

1H NMR, 13C NMR, and EPR spectra of six-coordinate ferric porphyrin complexes [Fe(Por)L2]ClO4 with different porphyrin structures are presented, where porphyrins (Por) are planar 5,10,15,20-tetraphenylporphyrin (TPP), ruffled 5,10,15,20- tetraisopropylporphyrin (TiPrP), and saddled 2,3,7,8,12,13,17,18- octaethyl-5,10,15,20-tetraphenylporphyrin (OETPP), and axial ligands (L) are weak oxygen ligands such as pyridine-N-oxide, substituted pyridine-N-oxide, DMSO, DMF, MeOH, THF, 2-MeTHF, and dioxane. These complexes exhibit the spin states ranging from an essentially pure high-spin (S = 5/2) to an essentially pure intermediate-spin (S = 3/2) state depending on the field strength of the axial ligands and the structure of the porphyrin rings. Reed and Guiset reported that the pyrrole-H chemical shift is a good probe to determine the spin state in the spin admixed S = 5/2,3/2 complexes (Reed, C. A.; Guiset, F. J. Am. Chem. Soc. 1996, 118, 3281-3282). In this paper, we report that the chemical shifts of the α- and β-pyrrole carbons can also be good probes to determine the spin state because they have shown good correlation with those of the pyrrole-H or pyrrole-Cα. By putting the observed or assumed pyrrole-H or pyrrole-Cα chemical shifts of the pure high-spin and pure intermediate-spin complexes into the correlation equations, we have estimated the carbon chemical shits of the corresponding complexes. The orbital interactions between iron(III) and porphyrin have been examined on the basis of these chemical shifts, from which we have found that both the d xy-a2u interaction in the ruffled Fe(TiPrP) L2+ and dxy-a1u interaction in the saddled Fe(OETPP)L2+ are quite weak in the high-spin and probably in the intermediate-spin complexes as well. Close inspection of the correlation lines has suggested that the electron configuration of an essentially pure intermediate-spin Fe(TiPrP)L2+ changes from (dxy, dyz)3(dxy) 1(dz2)1 to (dxy)2(d xz, dyz)2(dz2)1 as the axial ligand (L) changes from DMF to MeOH, THF, 2-MeTHF, and then to dioxane. Although the DFT calculation has indicated that the highly saddled intermediate-spin Fe(OETPP)-(THF)2+ should adopt (d xy, dyz)3(dxy)1(d z2)1 rather than (dxy)2(d xz, dyz)2(dz2)1 because of the strong dxy-aiu interaction (Cheng, R.-J.; Wang, Y.-K.; Chen, P.-Y.; Han, Y.-P.; Chang, C.-C. Chem. Commun. 2005, 1312-1314), our 13C NMR study again suggests that Fe(OETPP)(THF)2 + should be represented as (dxy)2(d xz, dyz)2(dz2)1 because of the weak dxy-aiu interaction. The contribution of the S = 3/2 state in all types of the spin admixed S = 5/2,3/2 six-coordinate complexes has been determined on the basis of the 13C NMR chemical shifts.

Factors affecting the electronic ground state of low-spin iron(III) porphyrin complexes

To determine the factors affecting the ground-state electron configuration of low-spin Fe(III) porphyrin complexes, we have examined the 1H NMR, 13C NMR, and EPR spectra of a series of low-spin bis-ligated Fe(III) porphyrin complexes [Fe(Por)L2]±, in which the positions of porphyrin substituents and the coordination ability of axial ligands are different. The seven porphyrins used in this study are meso-tetraalkylporphyrins (TRP: R ispropyl, cyclopropyl, or isopropyl), meso-tetraphenylporphyrin (TPP), meso-tetrakis(2,3,4,5,6-pentafluorophenyl)porphyrin, and 5,10,15,20-tetraphenyl-2,3,7,8,12,13,17,18-octaalkylporphyrins (ORTPP: R is methyl or ethyl). The porphyrin cores of TRP are more or less S4-ruffled depending on the bulkiness of the alkyl substituents, while those of ORTPP are highly S4-saddled. Three types of axial ligands are examined which have the following characteristics in ligand field theory: they are (i) strong σ-donating imidazole (HIm), (ii) strong σ-donating and weak π-accepting cyanide (CN-), and (iii) weak σ-donating and strong π-accepting tert-butyl isocyanide (tBuNC). In the case of the bis(HIm) complexes, only the isopropyl complex, [Fe(TiPrP)(HIm)2]+, has shown the less common (dxz, dyz)4(dxy)1 ground state; the other six complexes have exhibited the common (dxy)2(dxz, dyz)3 ground state. When the axial imidazole is replaced by cyanide, even the propyl and cyclopropyl complexes have shown the (dxz, dyz)4(dxy)1 ground state; the TPP and ORTPP complexes have still maintained the common (dxy)2(dxz, dyz)3 ground state. In the case of the bis(tBuNC) complexes, all the complexes have shown the (dxz, dyz)4(dxy)1 ground state. However, the contribution of the (dxz, dyz)4(dxy)1 state to the electronic ground state differs from complex to complex; the (dxz, dyz)4(dxy)1 contribution is the largest in [Fe(TiPrP)(tBuNC)2]+ and the smallest in [Fe(OETPPP)(tBuNC)2]+. We have then examined the electronic ground state of low-spin [Fe(OEP)(tBuNC)2]+ and [Fe(ProtoIXMe2)(tBuNC)2]+; OEP and ProtoIXMe2 represent 2,3,7,8,12,13,17,18- octaethylporphyrin and protoporphyrin-IX dimethyl ester, respectively. These porphyrins have a1u HOMO in contrast to the other seven porphyrins that have a2u HOMO. The 13C NMR and EPR studies have revealed that the contribution of the (dxz, dyz)4(dxy)1 state in these complexes is as small as that in [Fe(OETPP)(tBuNC)2]+. On the basis of these results, we have concluded that the low-spin iron(III) porphyrins that have (i) strong axial ligands, (ii) highly saddle shaped porphyrin rings, (iii) porphyrins with a1u HOMO, and (iv) electron withdrawing substituents at the meso positions tend to maintain the common (dxy)2(dxz, dyz)3 ground state.