Radical anion and dianion salts of titanyl macrocycles with acceptor substituents or an extended π-system

Maxim A Faraonov; Dmitri V Konarev; Alexey M Fatalov; Salavat S Khasanov; Sergey I Troyanov; Rimma N Lyubovskaya

doi:10.1039/c6dt04896j

Radical anion and dianion salts of titanyl macrocycles with acceptor substituents or an extended π-system

Dalton Trans. 2017 Mar 14;46(11):3547-3555. doi: 10.1039/c6dt04896j.

Authors

Maxim A Faraonov¹, Dmitri V Konarev¹, Alexey M Fatalov², Salavat S Khasanov³, Sergey I Troyanov⁴, Rimma N Lyubovskaya¹

Affiliations

¹ Institute of Problems of Chemical Physics RAS, Chernogolovka, Moscow region 142432, Russia. konarev3@yandex.ru.
² Institute of Problems of Chemical Physics RAS, Chernogolovka, Moscow region 142432, Russia. konarev3@yandex.ru and Moscow State University, Leninskie Gory, 119991 Moscow, Russia.
³ Institute of Solid State Physics RAS, Chernogolovka, Moscow region 142432, Russia.
⁴ Moscow State University, Leninskie Gory, 119991 Moscow, Russia.

PMID: 28240750
DOI: 10.1039/c6dt04896j

Abstract

Crystalline anionic salts of titanyl macrocycles with acceptor substituents or an extended π-system have been obtained for the first time: (PPN⁺)₂{O[double bond, length as m-dash]Ti^IV(PcCl₈^4-)}^2- (1), (PPN⁺){O[double bond, length as m-dash]Ti^IV(Nc˙^3-)}˙^-·2C₆H₄Cl₂ (2) and (PPN⁺)₂{O[double bond, length as m-dash]Ti^IV(AceTPrzPz^4-)}^2-·1.3C₆H₄Cl₂·0.8C₆H₅CN (3) where PPN⁺ is the bis(triphenylphosphoranylidene)ammonium cation, PcCl₈ - 2,3,9,10,16,17,23,24-octachlorophthalocyanine; Nc - 2,3-naphthalocyanine, AceTPrzPz - tetra(acenaphthenopyrazino)porphyrazine. Salts 1-3 were obtained in the reduction of the parent titanyl macrocycles by fluorenone ketyl in the presence of an excess of PPNCl in o-dichlorobenzene with following precipitation of crystals with n-hexane. Reduction of macrocycles in 1-3 is accompanied by the appearance of intense NIR bands in the solid spectra at 963-1159 nm. It has been found that the extended π-system with linear annulation in {O[double bond, length as m-dash]Ti^IV(Nc˙^3-)}˙^- provides the shift of the NIR band to smaller energies (1159 nm) in comparison with those in the spectra of {O[double bond, length as m-dash]Ti^IV(Pc˙^3-)}˙^- (995-998 nm). Reduction of macrocycles leads also to the alternation of C-N_imine bonds due to partial disruption of their aromaticity. The disruption is higher for the dianions in 1 and 3 in comparison with the radical anions in 2. One-dimensional π-π stacking chains and layers are formed in 1 and 3 with diamagnetic {O[double bond, length as m-dash]Ti^IV(PcCl₈^4-)}^2- and {O[double bond, length as m-dash]Ti^IV(AceTPrzPz^4-)}^2- dianions, respectively. Salt 2 contains nearly isolated [{O[double bond, length as m-dash]Ti^IV(Nc˙^3-)}˙^-]₂ dimers with a strong π-π interaction between paramagnetic radical anion macrocycles. As a result, a transition from the triplet to singlet state with antiparallel ordering of spins within the dimers is observed in 2 below 200 K.