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

Abstract

Crystalline anionic salts of titanyl macrocycles with acceptor substituents or an extended π-system have been obtained for the first time: (PPN){O[double bond, length as m-dash]Ti(PcCl)} (1), (PPN){O[double bond, length as m-dash]Ti(Nc˙)}˙·2CHCl (2) and (PPN){O[double bond, length as m-dash]Ti(AceTPrzPz)}·1.3CHCl·0.8CHCN (3) where PPN is the bis(triphenylphosphoranylidene)ammonium cation, PcCl - 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(Nc˙)}˙ 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(Pc˙)}˙ (995-998 nm). Reduction of macrocycles leads also to the alternation of C-N 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(PcCl)} and {O[double bond, length as m-dash]Ti(AceTPrzPz)} dianions, respectively. Salt 2 contains nearly isolated [{O[double bond, length as m-dash]Ti(Nc˙)}˙] 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.

Dianionic Titanyl and Vanadyl (Cation+)2[MIVO(Pc4−)]2− Phthalocyanine Salts Containing Pc4− Macrocycles

“…NIR bands were also observed in the spectra of salts with [Ti IV O(macrocycle 4À )] 2À dianions. [31] Furthermore, we found no EPR evidenceo ft he presence of an admixture of [V IV O(PcC 3À )]C À in the salts 3 and 5.T he spectra of 1, 2, and 4 have different Q-band splitting, and different weak bands are present in the NIR range ( Figure 1). It is thought that the presence of severali ndependentd ianions in the crystal structure with differentc ationic environments can affect the splitting pattern.T he four band splitting is not well pronounced in the spectrum of 2 (as well as 3 with [V IV O(Pc 4À )] 2À , Figure 2), whichc ontains three independent[ M IV O(Pc 4À )] 2À dianions, whereas this splittinga nd weak bands in the NIR range are very pronouncedi nt he spectra of 1, 4 ( Figure 1), and 5 containing only one independent [M IV O(Pc 4À )] 2À dianion.…”

Salt of Ring‐Reduced Iron(II) Octaethyltetrapyrazinoporphyrazine Containing Trimetallic Dianions with Peripherally Coordinated ZnCl2 Units: {FeII(TPyzPzEt8)4–(ZnCl2)2}2–

“…That leads to partial loss of aromaticity of the system and alternation of the C‐N meso bonds in such a way that two pairs of oppositely located C‐N meso bonds are elongated and two other pairs of oppositely located bonds are shortened. The difference between them is 0.06–0.08 Å , . There is no obvious alternation of the C‐N meso bonds in the TPyzPzEt 8 macrocycle in 1 in contrast to reduced tetrapyrazinoporphyrazine macrocycles.…”

“…Reduction of dianionic phthalocyanine and tetrapyrazinoporphyrazine macrocycle to the radical trianionic and tetraanionic state leads to a strong blue shift of both Soret and Q‐bands and the appearance of new bands in the NIR range at 930–1070 nm , . As a rule, the intensity of the NIR bands for the tetraanionic macrocycle is essentially weaker in comparison with that for the radical trianionic macrocycle , .…”

“…Shorter bonds are formed with meso ‐nitrogen atoms (N meso ) and longer bonds are formed with pyrazine (N pyrazine ) and pyrrole (N pyr ) nitrogen atoms. Reduction of unsubstituted metal‐free H 2 TPyzPz and Ti IV O(AceTPrzPz) is accompanied by the reduction of the macrocycle to di‐ and tetraanionic state for (H 2 TPyzPz) 2– and {Ti IV O(AceTPrzPz) 4– } 2– , respectively , . That leads to partial loss of aromaticity of the system and alternation of the C‐N meso bonds in such a way that two pairs of oppositely located C‐N meso bonds are elongated and two other pairs of oppositely located bonds are shortened.…”

“…TPyzPz macrocycle has stronger acceptor properties than phthalocyanines due to the presence of eight additional electronegative nitrogen atoms in the macrocycle . Only two anionic compounds of TPyzPzs are known now , . At the reduction of metal‐free tetrapyrazinoporphyrazine (H 2 TPyzPz) and titanyl tetra(acenaphthenapyrazino) porphyrazine {Ti IV O(AceTPrzPz)} by sodium fluorenone ketyl in the presence of cryptand[2.2.2] or PPNCl, crystalline compounds containing diamagnetic H 2 TPyzPz 2–[34] and {Ti IV O(AceTPrzPz 4– )} 2–[35] dianions were obtained.…”