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Several covalently linked tetraphenyl porphyrin trimers and tetramers bearing ethylene oxide bridges originating from the m and p positions of adjacent and/or opposite meso-aryl groups have been synthesized and characterized by fast atom bombardment mass spectroscopy, ¹H NMR, optical absorption and emission spectroscopies. The fully and partially metallated zinc(II) and copper(II) derivatives have been prepared and their photophysical properties are outlined. The steady-state and time-resolved fluorescence studies of the heterotrimers indicate efficient energy transfer from the ZnP to the H²P unit. The efficiency and rate of energy transfer are dependent on the number of free-base units in the hetero-oligomers and the geometrical position of the porphyrin units. The heterotrimers consisting of one, two and three zinc(II) centres bind 4,4″-bipyridyl in different modes as revealed by the nature of binding curves. The bipyridyl ligand functions as a chelate in the complexes of biszinc(II) porphyrin trimers while two bipyridyls bind to trizinc(II) porphyrin trimers with one ligand functioning as a chelate and another exhibiting monodentate coordination behaviour. The folding of two ZnP units is clearly seen in the complexes of bis and triszinc(II) trimers with bipyridyl, which is substantiated by molecular mechanics calculations. Axial ligation studies with trimers show that the preorganization of porphyrin hosts is necessary for recognition of the guest. The binding of bipyridyl to the trimers is followed by global conformational changes and this behaviour is analogous to activated complex binding in induced-fit enzymes.

The synthesis, characterization and crystal structure of the octanitro-substituted porphyrin 5,10,15,20-tetrakis(3,5-dinitrophenyl)porphyrin, H₂T(3,5-DNP)P, are described. The solid state structure has two porphyrins in the unit cell with eight pyridine solvates and is made up from columnar arrays of the porphyrins. X-ray crystal structure data: monoclinic, space group P1 2₁/n1, a = 14.9996(9) Å, b = 8.2489(5) Å, c = 24.818(2) Å, α = 90 °, β = 104.172(1) °, γ = 90 °, V = 2977.3(3) ų, d_calc = 1.440 g m^-3, Z = 2.

The saturated vapor pressures of tetraphenylporphyrin H₂TPP, its four-coordinated metallo-complexes MTPP (M ≡ Ni, Cu, Zn, Pd, Ag, Cd) and some phenyl-substituted derivatives H₂T(R)PP (R ≡ 2-, 3-, 4-CH₃; 2-, 4-F; 2-, 3-, 4-Cl; 3-, 4-Br; 3,5-C(CH₃)₃) have been measured using the inert gas flow method. The values of sublimation enthalpy Δ_subH_m and entropy Δ_subS_m are calculated. On the basis of the kinetic vapor pressure dependence, the start temperatures of thermal destruction of the investigated porphyrins are determined. The temperatures of melting of the tetraphenylporphyrin metallo-complexes measured by the DSC method are in linear correlation with the Δ_subH_m values. The correlation between the thermodynamic functions of porphyrin sublimation (Δ_subH_m, Δ_subS_m, Δ_subG_m) and the literature data on the crystal structure of the compounds is considered. The Δ_subH_m values obtained by some authors by different methods are compared with the results of our investigations. Possible reasons for discrepancies in the results are discussed.

A set of 45 acids or acid combinations was examined in the condensation of pyrrole + benzaldehyde (10 mM each in CH₂Cl₂) leading to meso-tetraphenylporphyrin (TPP). Initial screening experiments identified suitable acid catalysts and the optimal concentration (in terms of TPP formation) for each acid. Subsequent experiments followed the time course of reactions using the best conditions identified in the screening experiments. The reaction course was followed by monitoring reactions from 1 min to 24 h for the yield of TPP (by UV-vis and HPLC), the yields of N-confused tetraphenylporphyrin and tetraphenylsapphyrin (by HPLC), the quantity of unreacted benzaldehyde (by TLC), and the oligomer composition (by laser desorption mass spectrometry). Diverse acids (Brønsted or Lewis; soluble or insoluble) were found to provide yields of TPP ranging up to ~50%. Only 10 acids gave no TPP. In addition, N-confused tetraphenylporphyrin was found to be a ubiquitous byproduct, whereas tetraphenylsapphyrin was not widely observed. MgBr₂-etherate and CuCl₂ each catalyzed porphyrinogen formation and resulted in porphyrin metalation following oxidation and neutralization of the reaction mixture, thereby providing direct, one-flask syntheses of magnesium and copper porphyrins. Observations concerning the reaction course obtained from prior studies of TFA or BF₃-etherate catalysis have been found to be quite general across a broad range of acid catalysts. Collectively, these results show that many acids have potential utility in porphyrin syntheses.

We report the kinetics of CO binding to a series of substituted ferrous tetra(4-X-phenyl)porphyrins (X = CF₃, Cl, H, CH₃, OCH₃) in DMSO solvent using a mixture of 1,2-DMI/1-MeIm as proximal base. The CO dissociation rate constant increases with electron donation of the substituent X; the aggregate Hammett ρ value is -0.38. Using a Swain-Lupton analysis we determine the electronic effects to be transmitted 67% by through-bond or field effect and 33% by resonance. These results indicate that there is significant conjugation between the phenyl rings and the porphyrin core of iron tetraphenylporphyrin systems.

A donor-σ-acceptor compound incorporating tetrathiafulvalene and tetraphenylporphyrin units was synthesized. The structures of the target compound and its intermediates have been characterized by ¹H NMR, ESI MS, UV-vis, IR and mp. The results of UV-vis and cyclic voltammetry of the compound indicated negligible intramolecular charge transfer interaction in its ground state. The fluorescence and fluorescence lifetime of the compound were reduced, compared to tetraphenylporphyrin, which evidently indicated that photoinduced electron transfer occurred from the tetrathiafulvalene (TTF) unit to the tetraphenylporphyrin unit in the excited state. The fluorescence intensity of the compound could be reversibly modulated by sequential oxidation and reduction of the TTF unit using electrochemical and chemical methods. Therefore, a new fluorescence molecular switch based on TTF and porphyrin units was established.

This paper has scrutinized, both experimentally and theoretically, the conformation of an olefinic substituent on the pyrrole β-carbon of tetraphenylporphyrin. Compelling evidences collected from linear optical absorption and NOESY ¹H NMR experiment strongly suggest that, in solution, it is highly possible for the olefinic acceptor on pyrrole β-carbon to have a coplanar or near coplanar conformation with the pyrrole of the porphyrin core. This conformation ensures effective π-conjugation between the pyrrole ring and its olefinic substituent which is reflected in the linear absorption spectroscopy as the red-shifting of both Soret and Q-bands and possibly the splitting of the absorption Soret band. The intensified long wavelength absorption Q-band of the porphyrin is also consistent with the proposed π-conjugation. Regarding nonlinear optical absorption, an active nonlinear optical (NLO) response has been observed for these porphyrins, indicative of efficient electronic coupling (resonance interaction) between the electronic acceptor and porphyrin macrocyclic ring, compatible with a coplanar or near coplanar conformation in order to achieve π-conjugation. Such conformation of the peripherally appended olefinic acceptor has been further confirmed by INDO/1 Hamiltonian in the ZINDO computational calculations. The INDO/S electron density calculation further reveals that the range of intramolecular charge-transfer (ICT) does not encompass the whole porphyrin core but is mostly confined to the pyrrole ring attached to the olefin-linked acceptor. Furthermore, ICT characteristics were found to be more heavily involved in the Soret absorption band than Q-band. Our analysis of the porphyrin π-conjugation is consistent with modest solvatochromic behavior and the moderate NLO activity of the porphyrins compared with NLO chromophores with many less π-electrons.

trans-Diolchlorin was prepared by nucleophilic addition of methyl-Grignard bromide to meso-tetraphenyl-2,3-dioxoporphyrin, as its free base or Ni(II) complex. The trans-configuration of the vic-diol functionality was shown by single crystal X-ray diffractometry. The nickel complex of the trans-dimethyldiol proved susceptible to Pb(IV) acetate-induced, oxidative diol cleavage, generating a meso-tetraphenylsecochlorin bismethylketone Ni(II) complex, the first example of this chromophore class. Under Brønsted-basic conditions, this bisketone cyclized via an intramolecular aldol condensation to provide a meso-tetraphenyloxypyriporphyrin. Reduction of this porphyrin analog saturated the double bond in the pyridinone moiety, generating an oxypyrichlorin. Reaction of the meso-tetraphenylsecochlorin bismethylketone Ni(II) complex with Lawesson's reagent induced the formation of a thiomorpholinochlorin substituted with two methylene groups, the first example of any porphyrin analog containing a thiomorpholine moiety.

Mixing Cu(II)Cl₂ with free base tetraphenylporphyrin ((H₂(TPP)) in dry deaerated 1,2-dichloroethane surprisingly yields a mixture of Cu(II)(TPP) and Cu(III)(TPP). The later is long-lived in the absence of water and slowly decomposes within days to yield Cu(II)(TPP). Furthermore, in the presence of air, a slightly different Cu^III porphyrin species forms, presumably, Cu(III)(TPP)^•+, in which the Q-band is subject to a 10 nm red shift. The new Cu(III)(TPP) and Cu(III)(TPP)^•+ differ in terms of absorption, fluorescence, electron paramagnetic resonance (EPR), and X-ray photoemission spectroscopy (XPS) when compared to the well-characterized Cu(II)(TPP), Cu(II)(TPP)^•+, and Cu(II)(TPP)²⁺ species.

Emission-based oxygen sensing properties of highly luminescent tetraphenylporphyrin molecules were investigated in polystyrene, ethyl cellulose, poly(1-trimethylsilyl-1-propyne) and poly(isobutylmethacrylate) matrices. The effect of perfluorochemicals (PFCs) on oxygen sensitivity and stability of the sensor materials was also examined. Fluorescence intensity and lifetime measurements of meso-tetraphenylporphyrinato Zn(II) (ZnTPP) and meso-tetraphenylporphyrin (H₂TPP) materials were performed in the concentration range of 0–100% pO₂. The fluorescence intensity variation of H₂TPPvs. oxygen was 86%. H₂TPP-based composite also yielded higher Stern–Volmer constant, faster response and regeneration time, excellent long term photostability and larger linear response range with respect to ZnTPP. The detection limit of oxygen for H₂TPP was less than 0.5%. When stored in sealed bags protected from sunlight, no decrease in oxygen sensitivity was observed during approximately five months. As far as we know, the gathered utilization of PFCs and H₂TPP embedded in polymer matrices was not previously described in literature, and has present amelioration compared to materials already existing.

An improved method to obtain and purify the tetrasodium salts of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPP-pS4) and 5,10,15,20-tetrakis(3-sulfonatophenyl)porphyrin (TPP-mS4) is reported. With these substances as standards, the analysis of a typical reaction crude obtained in the sulfonation of tetraphenylporphyrin with hot sulfuric acid shows that the para/meta selectivity of sulfonation at each individual phenyl ring is 95:5. The pKa values of both TPP-pS4 and TPP-mS4 were spectrophotometrically measured (4.73 ± 0.01 and 4.85 ± 0.01 respectively). These results show that the sulfonato group has a stronger mesomeric electronic effect than the inductive one. The all-meta isomer of meso-tetrasulfonatophenylporphyrin in acidic aqueous solutions (10^-3–10^-4 M) shows a total absence of aggregation under the same experimental conditions in which its all-para counterpart is fully aggregated, as inferred from the typical Soret J- and H-aggregation bands characteristic of the supramolecular homoassociates. The effect of the number of meta-sulfonato groups on the structure of the aggregates at different length-scales is discussed.

Synthesis and isolation of selectively brominated tetraarylporphyrin derivatives is reported. Treatment with bromine of meso-5,10,15,20-tetrakis(3,4,5-trimethoxyphenyl)porphyrin (1) or meso-5,10,15,20-tetrakis(3,5-di-$t$-butyl-4-hydroxyphenyl)porphinatocopper(II) (2-Cu) yields products octabrominated at the 2,6-positions of meso-aryl substituents [5,10,15,20-tetrakis(2,6-dibromo-3,4,5-trimethoxyphenyl)porphyrin, ${}^{2,6}$Br₈1] or macrocyclic $\beta$-positions. The latter of these ($\beta$-brominated) was identified as the oxoporphyrinogen 2,3,7,8,12,13,17,18-octabromo-5,10,15,20- tetrakis(3,5-di-$t$-butyl-4-oxo-cyclohexa-2,5-dienylidene)porphyrinogen 3 obtained due to the adventitious oxidation and demetalation of 2-Cu, which could be alkylated at its macrocyclic nitrogen atoms yielding N${}_{21}$,N${}_{22}$,N${}_{23}$,N${}_{24}$-tetrakis(4-bromobenzyl)-2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(3,5-di-$t$-butyl-4-oxo-cyclo hexa-2,5-dienylidene)porphyrinogen 4. The former compound ${}^{2,6}$Br₈1 was complexed with Zn(II) (${}^{2,6}$Br₈1-Zn) or Cu(II) (${}^{2,6}$Br₈1-Cu) and could also be subjected to further bromination yielding 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2,6-dibromo-3,4,5-trimethoxyphenyl)porphyrin, Br${}_{16}$1. The effect on the electrochemical properties of the 2,6-bromophenyl-substituted porphyrin compounds over the more highly brominated products was assessed.

With the objective of developing an antitumor agent, the synthesis of a chromenopyrazoledione conjugated to a tetraphenylporphyrin is described. A complete conformational analysis of the novel porphyrin conjugate was performed using ab initio Hartree–Fock calculations at the 6-31G* level. The novel conjugate (14) shows stronger absorption intensity for both Soret and Q-bands than the free meso-tetraphenylporphyrin. It binds weakly but selectively to the cannabinoid receptor type-2. During the synthetic approach, a new tetraphenylporphyrin, 5-[4-(3,5-dioxomorpholino)phenyl]-10,15,20-triphenylporphyrin (10), has been characterized.

A meso-tetra-6b,10b-dihydrobenzo[j]cyclobut[a]acenaphthylene free-base porphyrin was synthesised and its photophysical, photochemical and electrochemical properties were compared with those of free-base meso-tetraphenylporphyrin. The frontier orbitals and the HOMO–LUMO energy gaps of both compounds were also determined. It was demonstrated that the meso6b,10b-Dihydrobenzo[j]cyclobut[a]acenaphthylene porphyrin retained the same properties as the tetraphenylporphyrin.

We have examined the effects of changing the temperature on the structure of a six-coordinate (tetraphenylporphinato)iron(II) complex, [Fe(TPP)(1-MeIm)(CO)] C${}_{\mathrm{\text{6}}}$H${}_{\mathrm{\text{6}}}$. In particular, we examined whether the coordination group parameters, $i.e$. the Fe–C and C–O parameters showed any effects. The study, carried out between 100 and 330 K, revealed no effect on those coordination group parameters. The axial Fe–N(Im) bond distance showed a small effect. The peripheral phenyl groups show a somewhat larger bond distance effect with bond distance increases of 0.02 to 0.03 Å. The population of the disordered solvent molecule favors one site as the temperature is lowered.