•We observed valence tautomerism in copper complex.•Antiferromagnetic spin interaction at low temperature was assumed.•The role of ligands was revealed.
Electronic structure of copper complexes with ...redox-active ligands was studied by XPS. The temperature dependence of the redistribution of electron and spin densities was shown. A low temperature anomaly of magnetic properties of the copper complex with redox-active ligands was detected. The observed two states of copper (Cu+1 and Cu+2) allowed proposing valence tautomerism («redox-isomer» copper complex). The donating role of nitrogen atoms was established in the copper complex with redox-active ligand. The role of ligands in the formation of the electronic structure of square-planar complexes was revealed.
A series of novel brightly emitting Eu3+ coordination compounds with 1,3-diketones bearing a thiophene moiety and a linear CnF2n+1 chain (n = 1–8) were synthesized and fully characterized. The ...dependence of back energy transfer (BET) processes on the fluorinated chain length of the ligand environment was investigated in detail. The rates of radiative, non-radiative, and BET processes were estimated by a complete set of spectroscopic methods, including temperature stimulated luminescence measurements. It was demonstrated that fluorination provided a remarkable increase in the photoluminescence quantum yield up to 58% along with an increase in sensitization efficiency from 45 to 86%. It was explained by the reduction of non-radiative relaxation on molecular oscillators. The probability of the BET process has a trend to decrease from 500 to 100 s−1 upon an extension of the diketone fluorinated chain. Moreover, the back energy transfer process occurs from the resonant level of Eu3+ ion to ligand triplet state T1 through activation energy barrier ΔEA between potential energy surfaces of T1 and 5D0 states. It was found that extension of the fluorinated chain in ligand alter the activation energy and frequency factor of BET. The influence of the both parameters on BET was studied. The results obtained give a fundamental basis for further rational design of highly efficient luminescent compounds of Eu3+ ions.
Display omitted
•Novel Eu3+ complexes with thiophene-based 1,3-diketones bearing perfluorinated chains were synthesized.•No noticeable saturation of luminescence quantum yield with extension of the fluorinated chain was observed.•An increase in the fluorinated chain length results in a dramatic decrease in the back energy transfer (BET) process rate.•An additional back energy transfer pathway from the Eu3+ ion to an excited ligand charge transfer state was observed.
Linking of the trinuclear pivalate fragment Fe2CoO(Piv)6 by the redox-active bridge Ni(L)2 (compound 1; LH is Schiff base from hydrazide of 4-pyridinecarboxylic acid and 2-pyridinecarbaldehyde, Piv– ...= pivalate) led to formation of a new porous coordination polymer (PCP) {Fe2CoO(Piv)6}{Ni(L)2}1.5 (2). X-ray structures of 1 and 2 were determined. A crystal lattice of compound 2 is built from stacked 2D layers; the Ni(L)2 units can be considered as bridges, which bind two Fe2CoO(Piv)6 units. In desolvated form, 2 possesses a porous crystal lattice (S BET = 50 m2 g–1, V DR = 0.017 cm3 g–1 estimated from N2 sorption at 78 K). At 298 K, 2 absorbed a significant quantity of methanol (up to 0.3 cm3 g–1) and chloroform. Temperature dependence of molar magnetic susceptibility of 2 could be fitted as superposition of χM T of Fe2CoO(Piv)6 and Ni(L)2 units, possible interactions between them were taken into account using molecular field model. In turn, magnetic properties of the Fe2CoO(Piv)6 unit were fitted using two models, one of which directly took into account a spin–orbit coupling of CoII, and in the second model the spin–orbit coupling of CoII was approximated as zero-field splitting. Electrochemical and electrocatalytic properties of 2 were studied by cyclic voltammetry in suspension and compared with electrochemical and electrocatalytic properties of a soluble analogue 1. A catalytic effect was determined by analysis of the catalytic current dependency on concentrations of the substrate. Compound 1 possessed electrocatalytic activity in organic halide dehalogenation, and such activity was preserved for the Ni(L)2 units, incorporated into the framework of 2. In addition, a new property occurred in the case of 2: the catalytic activity of PCP depended on its sorption capacity with respect to the substrate. In contrast to homogeneous catalysts, usage of solid PCPs may allow selectivity due to porous structure and simplify separation of product.
A series of polymer complexes of Gd(III) and Eu(III) with 3-furancarboxylic (HFur) and 5-nitro-2-furancarboxylic (HNfur) acids differed in the composition and coligands presented by solvent molecules ...(CH
3
OH/C
2
H
5
OH/H
2
O) is synthesized: Gd(Fur)
3
(CH
3
OH)(C
2
H
5
OH)
n
(
I
), Gd(Nfur)
3
(CH
3
OH)
2
n
· CH
3
CN (
II
), Eu(Fur)
3
(C
2
H
5
OH)
n
(
III
), and Eu(Nfur)
3
(H
2
O)
2
n
·3CH
3
CN (
IV
). According to the X-ray diffraction (XRD) data, all complexes are 1D coordination polymers in which the lanthanide cation has the coordination number 8 (LnO
8
) to form the environment as a doubly augmented triangular prism (
I
,
II
) or a square antiprism (
III
,
IV
). The supramolecular levels of the polymers are stabilized due to intra- and intermolecular hydrogen bonds between the coordinated solvent molecules and O atoms of the chelate-bound anions of the acid and via two types of noncovalent C–H…O and N–O…π interactions that significantly contribute to an additional stabilization of the crystal packings. The biological properties of complexes
I
,
II
, and
IV
are studied with respect to the model nonpathogenic strain
Mycolicibacterium smegmatis
.
The reaction of Cr(NO
3
)
3
•9H
2
O with sodium cyclobutane-1,1-dicarboxylate Na
2
(cbdc) was studied and the conditions for the formation and crystallization of Na
I
—Cr
III
carboxylate complexes in ...various media were found. The synthesis in water followed by the use of EtOH as a crystallization medium enables the isolation of the compound {Na
3
Cr(cbdc)
3
(EtOH)
2
(H
2
O)•H
2
O}
n
(
1
). The 2D polymeric structure of this compound is composed of mononuclear Cr(cbdc)
3
3−
units. The similar recrystallization from MeOH leads to the formation of the 2D polymer CaNa
2
Cr
2
(cbdc)
4
(H
2
O)
4
(OMe)
2
(MeOH)
2
n
(
2
) containing binuclear Cr
2
(cbdc)
4
(μ-OMe)
2
4−
units. A similar reaction in water in the presence of an excess of NaOH followed by the recrystallization from MeOH afforded crystals of the compounds {Na
4
Cr
2
(cbdc)
4
(H
2
O)
4
(OH)(OMe)•H
2
O}
n
(
3
) and {Na
4
Cr
2
(cbdc)
4
(H
2
O)
3
(MeOH)(OH)(OMe)•H
2
O}
n
(
4
) having similar 1D-polymeric structures. The reaction of Cr(NO
3
)
3
•9 H
2
O with Na
2
(cbdc) in MeOH followed by the benzene vapor diffusion into the reaction solution gave crystals of the compound {Na
3
Cr(cbdc)
3
(MeOH)
2
•0.5C
6
H
6
}
n
(
5
) having a 2D polymeric structure similar to that of compound
1
.
For the goal of preparing Li
I
–Cr
III
heterometallic coordination compounds, we studied the reaction of Cr(NO
3
)
3
·9H
2
O and Li
2
(cbdc) (obtained by the neutralization of LiOH·H
2
O and ...cyclobutane-1,1-dicarboxylic acid (H
2
cbdc)) interacting in the 1:3 ratio in aqueous and methanol solutions. It was found that synthesis in the aqueous medium and subsequent crystallization of the reaction solution results in a low yield (9%) of crystalline 2D polymeric compound {CaLi
6
Cr
4
(OH)
4
(cbdc)
8
(H
2
O)
16
·7H
2
O}
n
(
1
) formed due to the hydrolysis of a chromium(III) carboxylate complex and the introduction of Ca
2+
ions penetrating into the structure as impurities in the initial LiOH·H
2
O compound. The use of methanol as a solvent in a similar reaction and subsequent long-term aging leads to the formation of crystals of Li
5
Cr(cbdc)
4
(H
2
O)
5
n
(
2
, yield: 55%) whose 3D polymeric structure contains independent fragments with five Li
+
ions and does not contain Ca
2+
ions. The crystal structures of
1
and
2
are determined by single-crystal XRD (CCDC No. 2161744 (
1
), No. 2161745 (
2
)).
Compounds of three types, LnL
3
(C
2
H
5
OH) (Ln = Nd (
I
), Sm (
II
), Eu (
III
)), LnL
3
(H
2
O) (Ln = Gd (
IV
), Tb (
V
)), and DyL
2
(NO
3
)(C
2
H
5
OH)
2
(
VI
), were obtained by reactions of ...lanthanide nitrate with NaL (L
–
= 2,4-dichlorophenoxyacetate anion) in ethanol. The composition and structure of complexes
I
–
VI
were investigated by elemental and thermogravimetric analysis, IR spectroscopy, and X-ray diffraction (nos. 2311578 (
I
), 2311579 (
II
), 2311580 (
III
), 2311581 (
IV
), 2311582 (
VI
)). All compounds have a one-dimensional polymer structure in which metal atoms are connected by bridging carboxylate groups. The π–π interactions and intermolecular contacts between the chains give rise to a three-dimensional supramolecular structure.
Coordination compounds of cobalt and nickel with an azomethine ligand (a product of 4-benzoyl-3-methyl-1-phenylpyrazol-5-one and 2-aminophenol condensation) are prepared and studied by XRD. It is ...established that Co(II) ions under the reaction conditions are oxidized to Co(III) to form (Et
3
NH)CoL
2
·2H
2
O complexes, whereas Ni(II) ions form the (Et
3
NH)(H
3
L)NiL(HL)·H
2
O·Solv compound. The anionic part of the nickel complex is a supramolecular dimer
assembled due to hydrogen bonds. The complexes are studied by static magnetic susceptibility techniques. It is shown that the Co compound is diamagnetic; this is confirmed by the oxidation of this compound and indicates that the metal ion occurs in the low-spin state. Weak ferromagnetic interactions of Ni(II) ions through bridging hydrogen bonds are discovered.
The results of studying the heterometallic trinuclear {Co
Ln} and tetranuclear {Co
Li
2
} carboxylate coordination compounds are systematized. The methods of the syntheses are discussed, and the ...structures and magnetic properties are considered.
A procedure for the chemical immobilization of a new Zn
II
–Eu
III
heterobimetallic complex in the SiO
2
aerogel matrix has been developed. In this Zn–Eu complex, a peripheral non-luminescent Zn ion ...acts as a binder to a silica matrix and prevents direct interaction of rare-earth ions with OH− and NH− groups in the silica matrix, which would have a detrimental effect on the luminescence of lanthanides. The procedure includes the synthesis of complexes, co-gelation of the obtained complex with SiO
2
sol, the washing of lyogels, and their subsequent supercritical drying in CO
2
. The composition and properties of the obtained aerogels were investigated using a low-temperature nitrogen adsorption technique, helium pycnometry, FTIR, Raman, UV–visible, and luminescence spectroscopy, XPS, PXRD, SEM, TEM, TGA combined with mass spectrometry, and small-angle neutron scattering. The aerogels modified with the Zn
II
–Eu
III
complex demonstrated strong red luminescence upon excitation with UV light.
Highlights
An approach is proposed for anchoring heterobimetallic complexes to silica aerogel matriх.
In anchored complex, Zn atoms shield Eu from luminescence quenchers.
Silica aerogel modified with Zn–Eu complex demonstrated strong red luminescence.
