Molecular structure, optical and magnetic properties of metal-free phthalocyanine radical anions in crystalline salts (H2Pc˙−)(cryptand[2,2,2][Na+])·1.5C6H4Cl2 and (H2Pc˙−)(TOA+)·C6H4Cl2 (TOA+ is tetraoctylammonium cation)
Abstract:Ionic compounds containing radical anions of metal-free phthalocyanine (H2Pc˙(-)): (H2Pc˙(-))(cryptand[2,2,2][Na(+)])·1.5C6H4Cl2 (1) and (H2Pc˙(-))(TOA(+))·C6H4Cl2 (2) have been obtained as single crystals for the first time. Their crystal structures have been determined, and optical and magnetic properties have been investigated. The H2Pc˙(-) radical anions have a slightly bowl-like shape with four pyrrole nitrogen atoms located below the molecular plane, while four phenylene substituents are located above th… Show more
“…Potentially, upon the formation of the (FeCl 16 Pc) 2– dianions, the second electron can be localized on the iron atoms to form [Fe 0 Cl 16 Pc(2–)] 2– , or it can be transfered to the phthalocyanine macrocycles to form [Fe I Cl 16 Pc(3–)] 2– . The formation of negatively charged phthalocyanine macrocycles in the salts with radical anions of metal‐free phthalocyanine (H 2 Pc · – ) and some metal(II) phthalocyanines is accompanied by the appearance of an intense band in the NIR range9,21 [for example, in the spectrum of (H 2 Pc · – )(TOA + ) · C 6 H 4 Cl 2 (TOA + is the tetraoctylammonium cation) this band is observed at 1024 nm, Figure 5, a]. The spectrum of salt 2 is shown in Figure 5 (b).…”
Section: Resultsmentioning
confidence: 99%
“… Spectra of the (H 2 Pc · – )(TOA + ) · C 6 H 4 Cl 2 salt (a) with metal‐free phthalocyanine radical anions,9 salt 2 (b), and parent Fe II Cl 16 Pc (c) in KBr pellets. …”
Iron hexadecachlorophthalocyanine (Cl16Pc) salts with a layered arrangement of phthalocyanine (Pc) macrocycles were obtained by the reduction of FeCl16Pc with sodium fluorenone ketyl in the presence of PPNCl [PPN+: bis(triphenylphosphine)iminium cation] and TBABr (TBA+: tetrabutylammonium cation). (PPN+)[(FeICl16Pc)–]·0.78C6H4Cl2·0.22C6H14 (1) contains π–π stacking columns formed by dimerized (FeICl16Pc)– anions. The side‐by‐side arrangement of neighboring columns results in the formation of a layered iron hexadecachlorophthalocyanine structure. (TBA+)3{[(FeCl16Pc)2]3–} (2) contains hexagonal layers formed by [(FeCl16Pc)2]3– dimers and separated by TBA+ cations. The dimers bear –3 charge and, according to optical and X‐ray diffraction data, consist of a [FeI(Cl16Pc)]– monoanion and a [Fe0(Cl16Pc)]2– dianion. These anions are bonded in the dimer by a Fe–Fe bond of 2.899(4) Å length. It was shown that the negative charge in both anions is localized on the iron atoms to form FeI and Fe0, respectively, and no electron transfer to the hexadecachlorophthalocyanine macrocycles is observed. Magnetic data indicate the presence of only one S = 1/2 spin per [(FeCl16Pc)2]3– dimer. This result is in agreement with the formation of iron(I) and iron(0) hexadecachlorophthalocyanine anions, which have the iron atoms in d7 and diamagnetic d8 electron configuration, respectively. The spins of the iron(I) atoms are arranged in a hexagonal manner and only weakly interact, which results in a Weiss temperature of –1 K because of the long distances between them (>18 Å). Previously studied anionic salts with a columnar arrangement of [FeI(Cl16Pc)]– do not show EPR signals from FeI. In contrast, salt 2 shows an intense EPR signal with main components at g⟂ = 2.249 and g∥ = 1.989, which are characteristic of FeI with d7 electron configuration.
“…Potentially, upon the formation of the (FeCl 16 Pc) 2– dianions, the second electron can be localized on the iron atoms to form [Fe 0 Cl 16 Pc(2–)] 2– , or it can be transfered to the phthalocyanine macrocycles to form [Fe I Cl 16 Pc(3–)] 2– . The formation of negatively charged phthalocyanine macrocycles in the salts with radical anions of metal‐free phthalocyanine (H 2 Pc · – ) and some metal(II) phthalocyanines is accompanied by the appearance of an intense band in the NIR range9,21 [for example, in the spectrum of (H 2 Pc · – )(TOA + ) · C 6 H 4 Cl 2 (TOA + is the tetraoctylammonium cation) this band is observed at 1024 nm, Figure 5, a]. The spectrum of salt 2 is shown in Figure 5 (b).…”
Section: Resultsmentioning
confidence: 99%
“… Spectra of the (H 2 Pc · – )(TOA + ) · C 6 H 4 Cl 2 salt (a) with metal‐free phthalocyanine radical anions,9 salt 2 (b), and parent Fe II Cl 16 Pc (c) in KBr pellets. …”
Iron hexadecachlorophthalocyanine (Cl16Pc) salts with a layered arrangement of phthalocyanine (Pc) macrocycles were obtained by the reduction of FeCl16Pc with sodium fluorenone ketyl in the presence of PPNCl [PPN+: bis(triphenylphosphine)iminium cation] and TBABr (TBA+: tetrabutylammonium cation). (PPN+)[(FeICl16Pc)–]·0.78C6H4Cl2·0.22C6H14 (1) contains π–π stacking columns formed by dimerized (FeICl16Pc)– anions. The side‐by‐side arrangement of neighboring columns results in the formation of a layered iron hexadecachlorophthalocyanine structure. (TBA+)3{[(FeCl16Pc)2]3–} (2) contains hexagonal layers formed by [(FeCl16Pc)2]3– dimers and separated by TBA+ cations. The dimers bear –3 charge and, according to optical and X‐ray diffraction data, consist of a [FeI(Cl16Pc)]– monoanion and a [Fe0(Cl16Pc)]2– dianion. These anions are bonded in the dimer by a Fe–Fe bond of 2.899(4) Å length. It was shown that the negative charge in both anions is localized on the iron atoms to form FeI and Fe0, respectively, and no electron transfer to the hexadecachlorophthalocyanine macrocycles is observed. Magnetic data indicate the presence of only one S = 1/2 spin per [(FeCl16Pc)2]3– dimer. This result is in agreement with the formation of iron(I) and iron(0) hexadecachlorophthalocyanine anions, which have the iron atoms in d7 and diamagnetic d8 electron configuration, respectively. The spins of the iron(I) atoms are arranged in a hexagonal manner and only weakly interact, which results in a Weiss temperature of –1 K because of the long distances between them (>18 Å). Previously studied anionic salts with a columnar arrangement of [FeI(Cl16Pc)]– do not show EPR signals from FeI. In contrast, salt 2 shows an intense EPR signal with main components at g⟂ = 2.249 and g∥ = 1.989, which are characteristic of FeI with d7 electron configuration.
“…EPR and SQUID magnetic measurements were performed on polycrystalline samples of 1-11 sealed in 2 mm quarz tubes under 10 À5 Torr. (11) were obtained by the reduction of silver(II) phthalocyanine (25.8 mg, 0.042 mmol) by using excess of sodium fluorenone ketyl (16 mg, 0.0789 mmol) in the presence of TBABr (50 mg, 0.1551 mmol) for two hours at 100 8C until phthalocyanines were completely dissolved and a green solution had formed. The solution was cooled down to room temperature, stirred for two more hours, and filtered into a tube for diffusion.…”
Section: Discussionmentioning
confidence: 99%
“…[11] We analyzed magnetic properties of 1-11 by SQUID and EPR techniques on polycrystalline samples (Table 4 [25] The highest negative Weiss temperatures of À17 and À57 K were found for 7 and 8. [26,27] The g-factor of these salts drastically increased with decreasing temperature from g = 2.031 near room temperature to g = 2.292 at 20 K (g ?…”
Radical anion salts of metal-containing and metal-free phthalocyanines [MPc(3-)](·-), where M = Cu(II), Ni(II), H2, Sn(II), Pb(II), Ti(IV)O, and V(IV)O (1-10) with tetraalkylammonium cations have been obtained as single crystals by phthalocyanine reduction with sodium fluorenone ketyl. Their formation is accompanied by the Pc ligand reduction and affects the molecular structure of metal phthalocyanine radical anions as well as their optical and magnetic properties. Radical anions are characterized by the alternation of short and long C-Nimine bonds in the Pc ligand owing to the disruption of its aromaticity. Salts 1-10 show new bands at 833-1041 nm in the NIR range, whereas the Q- and Soret bands are blue-shifted by 0.13-0.25 eV (38-92 nm) and 0.04-0.07 eV (4-13 nm), respectively. Radical anions with Ni(II), Sn(II), Pb(II), and Ti(IV)O have S = 1/2 spin state, whereas [Cu(II)Pc(3-)](·-) and [V(IV)OPc(3-)](·-) containing paramagnetic Cu(II) and V(IV)O have two S = 1/2 spins per radical anion. Central metal atoms strongly affect EPR spectra of phthalocyanine radical anions. Instead of narrow EPR signals characteristic of metal-free phthalocyanine radical anions [H2Pc(3-)](·-) (linewidth of 0.08-0.24 mT), broad EPR signals are manifested (linewidth of 2-70 mT) with g-factors and linewidths that are strongly temperature-dependent. Salt 11 containing the [Na(I)Pc(2-)](-) anions as well as previously studied [Fe(I)Pc(2-)](-) and [Co(I)Pc(2-)](-) anions that are formed without reduction of the Pc ligand do not show changes in molecular structure or optical and magnetic properties characteristic of [MPc(3-)](·-) in 1-10.
“…[12] Now the salts with negatively charged cobalt(I), iron(I) and metal free phthalocyanines and porphyrazines have been obtained. [13][14][15][16][17][18][19] However, anionic phthalocyanines with tetra-coordinated metal atoms are not deeply investigated so far because of weak acceptor properties of metal phthalocyanine and as a result high air sensitivity of their anions. Metal-free phthalocyanines are reduced with potential more negative than -0.6 V, whereas zinc(II), copper(II), nickel(II) and manganese(II) phthalocyanines are reduced with potential -0.8 ÷ -0.9 V. [20] To increase the acceptor ability of metal macroheterocycles electron-withdrawing substituents such as Cl, F or CN can be attached to the phthalocyanine macrocycle or the number of nitrogen atoms in the macrocycle should be increased.…”
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