Hydrogen Atom Abstraction and Reduction Study of 21-Thiaporphyrin and 21,23-Dithiaporphyrin

The metal-free porphyrins protonation has gained interest over five decades because its structure modification and hardly monoacid intermediate isolation. Here, upon the hydrogen atom abstraction processes, one step diproptonated H3STTP(BF4)2 (STTP = 5,10,15,20-tetraphenyl-21-thiaporphyrin) (3) and stepwise protonated HS2TTPSbCl6 (5) and diprotonated H2S2TTP(BF4)2 (6) (S2TTP = 5,10,15,20-tetraphenyl-21,23-thiaporphyrin) compounds were obtained using HSTTP and S2TTP with oxidants. The closed-shell protonated compounds were fully characterized using XRD, UV-vis, IR and NMR spectra. In addition, the reduced 19π compounds [K(2,2,2)]HSTTP (2) and [K(2,2,2)]S2TTP (7) were synthesized by the ligands with reductant KC8 in THF solution. These two open-shell compounds were characterized with UV-vis, IR and EPR spectroscopies. The semiempirical ZINDO/S method was employed to analyze the HOMO/LUMO gap lever and identify the electronic transitions of the UV-vis spectra of the closed- and open-shell porphyrin compounds.

Crystalline paramagnetic supramolecular 2D-polymer of the tetra(4-pyridyl)porphyrin and terbium(iii) complex

A new crystalline hybrid organic–inorganic two-dimensional supramolecular polymer of the tetra(4-pyridyl)porphyrin and terbium(iii) complex, TbIII(TMHD)3, has been obtained and investigated.

Macrocycle- and metal-centered reduction of metal tetraphenylporphyrins where the metal is copper(II), nickel(II) and iron(II)

The reduction of metal(II) tetraphenylporphyrins, where metal(II) is copper, nickel or iron, has been performed in toluene solution in the presence of a cryptand. Cesium anthracenide was used as a reductant. Crystalline salts {cryptand(Cs⁺)}₂{Cu^II(TPP^4-)}^2- (1) and {cryptand(Cs⁺)}{Ni^I(TPP^2-)}^-·C₆H₅CH₃ (2) have been obtained. The two-electron reduction of {Cu^II(TPP^2-)}⁰ is centered on the macrocycle allowing one to study for the first time the structure and properties of the TPP^4- tetraanions in the solid state. Tetraanions have a diamagnetic state and show essential C-C_meso bond alternation. New bands attributed to TPP^4- appear at 670, 770 and 870 nm. Unpaired S = 1/2 spin is localized on Cu^II. The one-electron reduction of {Ni^II(TPP^2-)}⁰ centered on nickel provides the formation of {Ni^I(TPP^2-)}^- with unpaired S = 1/2 spin localized on Ni^I at 100(2) K. The effective magnetic moment of 2 is 1.68μ_B at 120 K and a broad asymmetric EPR signal characteristic of Ni^I is observed for 2 and also for (Bu₃MeP⁺){Ni^I(TPP^2-)}^-·C₆H₅CH₃ (3) in the 4.2-120 K range. Since dianionic TPP^2- macrocycles are present at 100(2) K, no alternation of C-C_meso bonds is observed in 2. The excited quartet S = 3/2 state according to the calculations is positioned close to the ground S = 1/2 state. In the excited state, charge transfer from Ni^I to the macrocycle takes place resulting in the formation of Ni^II with S = 1 and TPP˙^3- with S = 1/2 in the {Ni^II(TPP˙^3-)}^- anions. Therefore, the increase in the magnetic moment of 2 above 150 K is attributed to the population of the excited quartet state with a gap of 750 K. Salt 2 is EPR silent above 150 K and manifests absorption bands characteristic of TPP˙^3- at RT. The reduction of Ni^II(TPP^2-) and Fe^II(TPP^2-) by cesium anthracenide in the presence of Bu₃MeP⁺ yields crystals of 3 and (Bu₃MeP⁺){Fe^I(TPP^2-)}^-·C₆H₅CH₃ (4) whose crystal structures and optical properties are also presented. DFT calculations have been carried out for {M^II(TPP^2-)} (M = Cu, Ni and Fe) and their anions to interpret the experimental results obtained for 1-4.

Interaction of InIIIClPc and TlIIIClPc phthalocyanines with deprotonated porphyrin HTPP− anions. Metal-centred reduction of TlIIIClPc

Reactions of In[Formula: see text]ClPc or Tl[Formula: see text]ClPc phthalocyanines with monodeprotonated tetraphenylporphyrin HTPP[Formula: see text] anions have been studied under reduction or in the presence of [Formula: see text]-methylimidazole ([Formula: see text]-MeIm). Formation of salt {In[Formula: see text]-MeIm)2(TPP[Formula: see text]}[Formula: see text]{In[Formula: see text](Pc[Formula: see text]}[Formula: see text] ⋅ 4C6H4Cl2 (1) justifies partial abstraction of indium(III) atoms from In[Formula: see text]ClPc to form cationic {In[Formula: see text](TPP[Formula: see text]}[Formula: see text] porphyrins[Formula: see text]solvated by [Formula: see text]-MeIm and double-decker {In[Formula: see text](Pc[Formula: see text]}[Formula: see text] anions. Crystals of Tl[Formula: see text](HTPP[Formula: see text] (2) have been only obtained at the interaction of HTPP[Formula: see text] with Tl[Formula: see text]ClPc under reduction indicating that Tl[Formula: see text] is reduced to Tl[Formula: see text] and is abstracted by HTPP[Formula: see text]. To confirm the possibility of Tl[Formula: see text] formation under reduction we have studied reduction of Tl[Formula: see text]ClPc by sodium fluorenone in the presence of cryptand[2.2.2]. Crystals of {Cryptand(Na[Formula: see text]}(Tl[Formula: see text](Pc[Formula: see text]}[Formula: see text] ⋅ C6H4Cl2(3) have been isolated indicating metal-centered reduction of Tl[Formula: see text]ClPc to form Tl[Formula: see text] and preserving dianionic Pc[Formula: see text] macrocycles. Optical spectra and structures of the obtained compounds are discussed and compared with those of pristine M[Formula: see text]ClPc. It is shown that 1–3 are EPR silent due to the formation of diamagnetic components.

Dianionic States of Trithiadodecaazahexaphyrin Complexes with Homotrinuclear MII3O Clusters (M = Ni and Cu): Crystal Structures, Metal- Or Macrocycle-Centered Reduction, and Doublet-Quartet Transitions in the Dianions

Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain M^II₃O clusters inside a π-extended trianionic (Hhp^3-) macrocycle have been prepared. Studies of the magnetic properties of Ni^II₃O(Hhp) and Cu^II₃O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp^3-) macrocycle and diamagnetic Ni^II₃(O^2-) or paramagnetic Cu^II₃(O^2-) tetracations. The positive charge of M^II₃O(Hhp) is compensated by one acetate anion {M^II₃O(Hhp)}⁺(CH₃CO₂^-). The three-electron reduction of {M^II₃O(Hhp)}⁺ yields {cryptand(Cs⁺)}₂{Ni^II₂Ni^IO(Hhp^5-)}^2-·2C₇H₈ (1) and {cryptand(Cs⁺)}₂{Cu^II₃O(Hhp^•6-)}^2-·C₇H₈ (2) crystalline salts. The magnetic properties of 1 reveal the formation of Hhp^5- and the reduction of nickel(II) to the paramagnetic Ni^I ion (S = 1/2), which is accompanied by the formation of the {Ni^II₂Ni^IO(Hhp^5-)}^2- dianion. As a result, the magnetic moment of 1 is 1.68 μ_B in the 20-220 K range, and a broad EPR signal of Ni^I was observed. The Hhp^5- macrocycle has a singlet ground state, but the increase in the magnitude of the magnetic moment of 1 above 220 K is attributed to the population of the triplet excited state in Hhp^5-. The {Ni^II₂Ni^IO(Hhp^5-)}^2- dianion is transferred from the doublet excited state to the quartet excited state with an energy gap of 1420 ± 50 K. Salt 1 also shows an unusually strong low-energy NIR absorption, which was observed at 1000-2200 nm. In 2, a highly reduced Hhp^•6- radical hexaanion (S = 1/2) coexists with a Cu^II₃(O^2-) cluster (S = 1/2) in the {Cu^II₃O(Hhp^•6-)}^2- dianions. The dianions have a triplet ground state with antiferromagnetic exchange between two S = 1/2 spins with J = -6.4 cm^-1. The reduction of Hhp in both salts equalizes the initially alternated C-N bonds, supporting the increase in the Hhp macrocycle electron delocalization.

Reaction of GaIIIClPc, SnIVCl2TPP and BIIIClSubPc with cyanide anions: reduction of macrocycles vs. formation of cyano-containing macrocyclic anions

The reaction of GaIIIClPc, SnIVCl2TPP and BIIIClSubPc containing phthalocyanine (Pc), tetraphenylporphyrin (TPP) and subphthalocyanine (SubPc) macrocycles with cyanide in the presence of cryptand[2.2.2] under anaerobic conditions yields crystalline salts in which cyano anions substitute chloride anions at GaIII, SnIV or BIII, as well as reducing the macrocycles or adding one or two CN- to them. The reaction of GaIIICl(Pc2-) with CN- yields {crypt(K+)}{GaIIICN(Pc˙3-)}˙-·0.5C6H4Cl2 (1) in which the Pc2- macrocycle is reduced to Pc˙3-. Such reduction could probably occur through the addition of CN- to Pc2- forming {GaIII(CN)[Pc(CN)]3-}- which can decompose further interacting with an excess of CN-. As a result, Pc˙3- and cyanogene anions are formed. The interaction of SnIVCl2(TPP2-) with CN- is accompanied by the addition of CN- to the meso-carbon atom of porphyrin forming diamagnetic TPP(CN)3- macrocycles in {crypt(K+)}{SnIV(CN)2[TPP(CN)]3-}- (2). Salt 2 shows a strong NIR absorption band with the maximum at 854 nm whose intensity is comparable with that of the Soret band. The interaction of BIIICl(SubPc2-) with three equivalents of CN- is accompanied by the addition of two CN- to carbon atoms of SubPc2- closest to meso-nitrogen atoms forming {BIII(CN)[SubPc(CN)2]4-}2-. Most probably these dianions transfer electrons to C6H4Cl2 producing the {BIII(CN)[SubPc(CN)2]˙3-}˙- radical anions which form σ-bonded diamagnetic dianions in {crypt(K+)}2{BIII(CN)[SubPc(CN)2]}22-·3C6H4Cl2 (3). The remaining carbon atom closest to the meso-nitrogen atom is involved in this dimerization. According to the calculations, the energy of the C-CN bond is minimal for {GaIII(CN)[Pc(CN)]3-}- enabling further transformation of these anions to {GaIIICN(Pc˙3-)}˙- in 1, whereas cyano-containing anions in 2 and 3 with higher energy of this bond are stable towards the elimination of CN. Optical and magnetic properties of 1-3 together with their crystal and molecular structures are presented. The possible ways of the formation of 1-3 are discussed based on DFT calculations.