Photocatalytic reactions of metal diphthalocyanine complexes

Photocatalytic reactions of tin diphthalocyanine, Sn ^IVPc₂ and anionic form of Nd^III, Dy^III, Eu^III, Tm^III and Lu^III diphthalocyanine complexes ( [Pc(-2)Nd^IIIpc(-2)]⁻ , [Pc(-2)Dy^IIIPc(-2)]⁻ , [Pc(-2)Eu^IIIPc(-2)⁻, [Pc(-2)Tm^IIlPc(-2)r and [Pc(-2)LuIIIpc(-2)]⁻ respectively) in the presence of CH₂CI₂, S0₂, pentachlorophenol (PCP), 4-chlorophenol (4-Cp) and thionyl chloride have been studied. Photoreactions involving lanthanide diphthalocyanines, filtered and unfiltered radiations were employed, whereas for photoreactions involving tin diphthalocyanine, only unfiltered radiation was employed. For lanthanide diphthalocyanine complexes, LnPce-, the photosensitization power increases with the decrease of the lanthanide ionic radii, implying that the photocatalytic activity of LnPc₂⁻ complexes is associated with the π-π interaction between both phthalocyanine rings. Thus, LuPc₂⁻ is a better photocatalyst than other lanthanide diphthalocyanine complexes. Photolysis ofSnPc₂ in an acetonitrile/dichloromethane solvent mixture, using unfiltered radiation from a tungsten lamp, results in the one-electron oxidation of this species to [Pc( -2 )Sn(IV)Pc(-1)]⁻. The relative quantum yields for the disappearance of SnPc₂ are in the order of 10⁻¹. The photoreaction of SnPc₂ is preceded by excitation to nπ* excited states, before been ,quenched by CH₂CI₂. The one-electron oxidation species, [Pc(-2)Sn(lV)pc(-1)]⁻ was also formed during the photolysis of SnPc₂ in dichloromethane containing S0₂, and with quantum yields of order of 10⁻³. Visible photolysis of [Pc( -2)Nd^IIIpc(-2)]⁻, [Pc(-2)Dy^IIIPc(-2)]⁻ and [Pc(-2)Lu^IIIpc(-2)]⁻ in N,N. dimethylformamide (DMF)/dichloromethane solvent mixture containing SO₂, results in the formation of the one-electron oxidation species, Pc(-2 )Nd^IIIpc(-1), Pc( -2) Dyi^IIIPc(-1) and Pc(-2)Lu^IIIpc(-1), respectively. The relative quantum yields are in the order of 10². The photoreactions are preceded by population of the excited triplet state,³π-π* [ LnPc₂]⁻ complex, before exchanging an electron with S0₂. The one-electron oxidation species of Dy^III and Lu^III diphthalocyanine complexes have also been formed from visible photolysis of [Pc(-2 )Dy^IIIPc(-2)]⁻and [Pc(-2)Lu^IIIpc(-2)]⁻in acetonitrile containing PCP. The PCP is reductively dechlorinated to tetra- and trichlorophenols. The quantum yields for the photosensitization reactions are in the order of 1 0⁻. Photolysis, using visible radiation from 220 W Quartzline lamp, of an aqueous solution of 4-Cp, saturated with oxygen and containing a suspension of solid [Pc(-2)Nd^IIIpc(-2)]⁻, results in the formation of benzoquinone, hydro quinone and 4-chlorocatechol. The quantum yields for the degradation of 4-Cp are in the order of 10⁻. Langmuir-Hinshelwood kinetic model shows the adsorption of 4-chlorophenol onto solid [Pc(-2)Nd^IIIpc(-2)]⁻. Lanthanide diphthalocyanine complexes ([Pc-2)Nd^IIIpc(-2)]⁻. [Pc(-2)Eu^IIIpc(-2)]⁻, (Pc(-2)Tm^IIIpc( -2)]⁻ and (Pc(-2)Lu^IIIpc(-2)]⁻) undergo one or two-electron oxidation in the presence of thionyl chloride. At low concentrations of SOCI₂(10⁻² mol dm⁻³), direct two-electron oxidation of the (Pc(-2 )LnPc - 2)]⁻ species to (Pc(-1)LnPc(-1)]⁻ occurs. Spectroelectrochemical behaviours of Sn^IVPc₂ have been also studied. The cyclic voltammetry ofSnPc₂ in CH₂CI₂/TBAP show two reduction couples at -0.56 V and -0.89 V versus saturated calomel electrode (SCE) and one oxidation couple at 0.35 V versus SCE. In DMFITEAP system, the reduction couples are observed at -0.44 V and -0.81 V versus SCE whereas the oxidation couple occurred at 0.43 V versus SCE. The oxidation couple corresponds to [Pc(-2 )Sn^IVPc(-2 )]/[Pc(-2)Sn^IVPc( -I)] . and the reduction couples to [Pc(-2)Sn^IVPc( -2 )]/[Pc(-2 )Sn^IVPc( -3 )]⁻ and [Pc(-2)Snl^IVPc( -3)] ⁻/[Pc(-3 )Sn^IVPc(-3)]²⁻, respectively. The electronic absorption spectra of these reduced and oxidized species are reported

Photosensitization reactions of neodymium, dysprosium and lutetium diphthalocyanine

Photolysis, using a visible radiation, of diphthalocyanine complexes of NdIII, DyIII and LuIII ([Pc(−2)NdIIIPc(−2)]−, [Pc(−2)DyIIIPc(−2)]− and [Pc(−2)LuIIIPc(−2)]−, respectively) in the presence of pentachlorophenol (PCP) or SO2 results in the one-electron oxidation of the diphthalocyanine species to Pc(−1)NdIIIPc(−2), Pc(−1)DyIIIPc(−2) and Pc(−2)LuIIIPc(−2), respectively. The PCP is reductively dechlorinated to tetra- and trichlorophenols. The quantum yields for the photosensitization reactions are of the order 10−4

Spectroelectrochemical studies of tin (IV) diphthalocyanine

Cyclic voltammetry of tin(IV) diphthalocyanine (Pc2Sn) in dichloromethane containing TEAP shows two reduction couples at −0.56 and −0.89 versus saturated calomel electrode (SCE) and one oxidation couple at 0.35 V versus SCE; all were quasireversible one-electron couples. The oxidation couple corresponds to [Pc(−1)SnIVPc(−2)+/Pc(−2)SnIVPc(−2) and the reduction couples to Pc(−2)SnIVPc(−2)/[Pc(−3)SnIVPc(−2)]− and [Pc(−3)SnIVPc(−2)]−/[Pc(−3)SnIVPc(−3)]2−, respectively. The electronic absorption spectra of the various reduced or oxidized tin(IV) diphthalocyanine species are reported

Photoassisted reduction of thionyl chloride by neodymium, europium, thulium and lutetium diphthalocyanines

Diphthalocyanine complexes of Nd III, EuIII, TmIII and LuIII ( [Pc (−2) Nd IIIPc (−2) ] −, [Pc (−2) EuIIIPc (−2) ] −, [Pc (−2) TmIIIPc (−2) ] − and [Pc (−2) LuIIIPc (−2) ] −, respectively) , undergo one or two-electron oxidation in the presence of thionyl chloride. The oxidation products depend on the concentration of the thionyl chloride. At low concentrations of SOCl2 (larger than 10−4 mol dm−3) one-electron oxidation occurs only upon photolysis, giving the neutral lanthanide diphthalocyanine, Pc (−2) LnPc (−1) , complexes. The Pc (−2) LnPc (−1) species undergo one-electron photooxidation to the [Pc (−1) LnPc (−1) ] + in dichloromethane and in the presence of SOCl2. At large concentrations of SOCl2 (>10−2 mol dm−3) , two electron oxidation of the [Pc (−2) LnPc (−2) ] − species directly to [Pc (−1) LnPc (−1) ] + occurs

Photocatalytic properties of neodymium diphthalocyanine towards the transformation of 4-chlorophenol

Photolysis of aqueous solutions of 4-chlorophenol (4-Cp) in the presence of solid neodymium diphthalocyanine ([Pc(−2)NdPc(−2)]−) and oxygen using visible and ultraviolet (UV) radiation resulted in the formation of a number of products. For photolysis in the visible region, phenol, benzoquinone, hydroquinone were observed as intermediates and 4-chlorocatechol (4-CC) as the main product; intermediates similar to those observed for visible photolysis were obtained. Langmuir–Hinshelwood kinetic model was used for treatment of photochemical data

Photochemically induced electron transfer between sulfur dioxide and tin (IV) mono-and di-phthalocyanines

Photolysis, using radiation from a tungsten lamp, of tin diphthalocyanine (Pc2Sn(IV)) in dichloromethane containing SO2 results in the one-electron oxidation of this species to [Pc(−2)Sn(IV)Pc(−1)]+. The relative quantum yields for the formation of the oxidized species were in the order of 10−3. The one-electron oxidized complex was also formed when Pc2Sn was photolysed in an acetonitrile/dichloromethane solvent mixture. Photolysis of the monomeric (L)2Sn(IV)Pc(LOH−, Cl−, Br− and F−) in pyridine and in the presence of SO2 resulted in the reduction of these species to (L)2Sn(IV)Pc(−3)]− with quantum yields in the order of 10−2