Homotrinuclear complexes were synthesized by reaction of [30]trithiadodecaazahexaphyrine (hemihexaphyrazine) with nickel(II), copper(II) or manganese(II
Different tautomeric structures of thiadiazole annelated hemihexaphyrazine (TDAHHp hemihexaphyrazine -2,3,5,10,12,13,15,20,22,23,25,30-dodecaazahexaphyrin (C 30 -ченного гемигексафиразина -2,3,5,10,12,13,15,20,22,23,25,30-додекаазагексафирина (C 30 H 15 N 15 S 3
Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain M II 3 O clusters inside a π-extended trianionic (Hhp 3− ) macrocycle have been prepared. Studies of the magnetic properties of Ni II 3 O(Hhp) and Cu II 3 O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp 3− ) macrocycle and diamagnetic Ni II 3 (O 2− ) or paramagnetic Cu II 3 (O 2− ) tetracations. The positive charge of M II 3 O(Hhp) is compensated by one acetate anion {M II 3 O(Hhp)} + (CH 3 CO 2 − ). The three-electron reduction of {M II 3 O(Hhp)} + yields {cryptand 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 II 2 Ni I O(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 II 2 Ni I O(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 II 3 (O 2− ) cluster (S = 1/2) in the {Cu II 3 O(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.
Hemihexaphyrazines can be considered as hexamembered porphyrinoids of the ABABAB type, where thiadiazole rings (A) and pyrrole-containing subunits (B) joined via aza bridges to form a macrocyclic system with an expanded coordination cavity capable of holding at once three atoms of transition metals that are formed a triangular cluster. It was established for the first time that unsubstituted hemihexaphyrazine and its metal complexes can be reduced to form crystalline salts. These salts were characterized by UV-Vis-NIR and IR spectroscopy, MS, and X-Ray diffraction data. The magnetic properties of these compounds were studied for the first time using EPR and SQUID techniques within the [Formula: see text] K temperature range. It was shown that the three-electron reduction of starting [Formula: see text] yields [Formula: see text] and [Formula: see text] crystalline salts. An unusual doublet-quartet transition was found for the [Formula: see text] dianions. Salt [Formula: see text] also shows an unusually strong low energy NIR absorption, which was observed at 1000–2200 nm with maxima located at 1283 and 1980 nm. A phenomenon consisting of equalization of bond lengths among exocyclic nitrogen atoms ([Formula: see text] and neighboring atoms C(pyrrole) and C(thiadiazole) was observed under reduction conditions.
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