A new copper(
ii
) complex (
I
) was obtained by the reaction of a sterically crowded 2,4-di-(
tert
-butyl)-9-chloro-benzo5,61,4oxazine2,3-
b
phenoxazine bridging ligand with Cu(
ii
) ...hexafluoroacetylacetonate. Compound
I
is a quasi-one-dimensional complex in which the Cu(hfac)
2
moieties are co-crystallized with the triphenodioxazine molecules through only weak Cu N short intermolecular interactions (the Cu N distances are 2.732 and 2.752 Å). The magnetic AC susceptibility data show that in spite of the absence of zero-field splitting in the Cu(
ii
) ion with
S
= 1/2, the compound demonstrates a slow magnetic relaxation behaviour at a weak applied magnetic field (
H
DC
= 500 Oe). The EPR spectra and DC magnetic measurements show the strong axial anisotropy of the g-tensor. The temperature dependence of the relaxation time is well described by the combination of one-phonon direct and two-phonon Raman processes.
A new copper(
ii
) complex (
I
) was obtained by the reaction of a sterically crowded 2,4-di-(
tert
-butyl)-9-chloro-benzo5,61,4oxazine2,3-
b
phenoxazine bridging ligand with Cu(
ii
) hexafluoroacetylacetonate.
Two new copper( ii ) complexes have been obtained by the reaction of sterically crowded triphenodioxazine ligands with Cu( ii ) hexafluoroacetylacetonate. Compound 1 is a co-crystal of Cu(hfac) 2 ...moieties and triphenodioxazine molecules within a quasi-one-dimensional crystal structure with only weak Cu⋯N short intermolecular interactions (Cu⋯N distances are equal to 2.69(1) and 2.75(1) Å). In contrast, complex 2 has a binuclear structure with two Cu(hfac) 2 units bridged through triphenodioxazine ligand with the covalent Cu–N bond length of 2.335(2) Å. The magnetic AC susceptibility data show that in spite of the absence of zero-field splitting in the Cu( ii ) ion having the ground state with spin S = 1/2, both compounds demonstrate slow magnetic relaxation at the applied magnetic field. For a quasi-one-dimensional complex 1, the optimal field for observing slow magnetic relaxation is 400 Oe, while for the binuclear complex it is 2500 Oe. The observed temperature dependence of the relaxation time in 1 is well described by the combination of Raman and direct mechanisms of relaxation, while for complex 2 the inclusion of Raman mechanism and quantum tunneling of magnetization is required to describe the relaxation behavior.
The reaction of 4,6-di-
tert
-butyl-3-nitrocyclohexa-3,5-diene-1,2-dione with secondary amines (piperidine, morpholine, 1-methylpiperazine) in isopropanol involves Michael addition and ANRORC and ...forms a mixture of products. The resulting compounds were characterized by IR and
1
H and
13
C NMR spectroscopy, and elemental analysis. The molecular structures of 3-nitrocyclohexa-3-ene-1,2-dione and cyclopenta-1,3-diene derivatives were established by X-ray diffraction analysis.
Reactions of 12
H
-quinoxaline2,3-
b
phenoxazine (QOPO) derivatives with the Co
II
and Zn
II
hexafluoroacetylacetonates accompanied by protonation of the starting bases result in stable complexes ...QOPOH
+
M(hfac)
3
−
whose structure was determined by X-ray diffraction and by
1
H and
15
N NMR spectroscopy. The complexes are characterized by long-wavelength absorption (560–664 nm) and fluorescence in the red region (λ
fl
= 674–805 nm). The relative energies of the protonated tautomers
N(14)—H
and
N(7)—H
were determined using the results of B3LYP–D3BJ/6-311G++(d,p) density functional calculations with inclusion of D3BJ dispersion correction. A SQUID magnetometry study of the static and dynamic magnetic properties of the Co
II
complex revealed that it behaves as a field-induced single-ion magnet.
Zinc(II) complexes
2
,
3
, and
5
with redox-amphoteric
o
-indophenol ligands were prepared. The molecular structures of tetracoordinate complex
2
and hexacoordinate complex
3
were determined by ...single-crystal X-ray diffraction. The antioxidant properties of indophenols and their complexes were studied by cyclic voltammetry (CVA) and EPR spectroscopy. Complexation of indophenols increases the oxidation potentials by more than 0.84 V and leads to the formation of stable metal-containing radicals.
A series of new derivatives comprising heteropentacyclic 12
H
-quinoxalino2,3-
b
-phenoxazine (QOPO) system and functionalized with arylamide anchoring groups was synthesized. Their photostability as ...well as the spectral, luminescent, electrochemical, and optoelectronic properties were studied both in composites prepared by adsorption of QOPO onto the TiO
2
surface and in solution. Attachment of the amide anchoring groups to the QOPO core provides high adsorption of the compounds and the onset of photovoltaic properties that were not observed in the unfunctionalized precursors. However, these groups do not provide efficient injection of excited electrons into the conduction band of the semiconductor. According to B3LYP/6-311++G(d,p) density functional calculations of the model nanoclusters QOPO/(TiO
2
)
10
, efficient electron injection and, as a consequence, high photovoltaic conversion efficiency of dye-sensitized solar cells require delocalization of the LUMO of the QOPO/TiO
2
system over both structural fragments. Relevant anchoring groups are proposed.
The Сd(II) complexes with redox amphoteric 2,6-di-(
tert
-butyl)-4-((2-hydroxyphenyl)imino)cyclohexa-2,5-dienone ligands L
1
and L
2
(adducts
I
,
II
, and
III
) are synthesized. The structures of ...coordinated complexes
I
,
II
, and
III
are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 1838319 (
II
) and 1838310 (
III
)) and confirmed by the
1
Н,
13
С, and
113
Cd NMR spectroscopy (for complexes
I
and
III
) and IR spectroscopy data.
A radical stable at room temperature was prepared by the oxidation of a toluene solution of 6,8-di-(
tert
-butyl)-3
H
-phenoxazin-3-one oxime with lead oxide PbO
2
. The DFT/B3LYP/6-311++G**,
ab ...initio
MP2/def2-svp, and CASSCF (15,15)/def2svp calculations showed the ground structure of the radical in which the spin density is concentrated on the heterocyclic nitrogen atom and energetically close electromeric form in which the spin density is predominantly localized on the exocyclic nitroso group. Two forms of the radical are the first example of electronic isomerism in the series of electroneutral organic structures.
New sterically crowded quinoxalinophenoxazine derivatives containing a crown ether fragment have been synthesized and found to exhibit strong luminescence. The synthesized heteropentacenes are ...interesting as potential biomarkers of ion exchange processes.
Complex formation reaction of redox-active 2,4,6,8-tetra(
tert
-butyl)phenoxazin-1-one with cobalt(II) chloride leading to the dimeric adduct has been studied. UV spectroscopy studies have revealed ...the equilibrium of the formed adduct with dissociated form of the complex in the acetonitrile solution. In the presence of ethylene glycol, the complex formation with cobalt(II) perchlorate has afforded the high-spin trimolecular adduct. Crystal structure of the obtained adducts has been studied by means of X-ray diffraction analysis.
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