Vladimir M. Amirkhanov

Oxime analogs of amino acids and peptides are efficient ligands for NiII ions

Abstract Oxime derivatives of amino acids, amides, and peptides are very efficient ligands for NiII ions forming very stable water-soluble complexes. Oxime of amino acids amides forms octahedral and square-planar complexes with the same 4N coordination mode. The spectroscopic and X-ray diffraction studies indicate an unusual role for the hydrogen bond in NiH−1L2 species, which stabilizes the cis coordination of two ligands in a planar complex. Oxime analogs of natural amino acid can be much more efficient ligands than the parent molecules.

X-Ray analysis and excited state dynamics in a new class of lanthanide mixed chelates of the type LnPhβ3·Phen (Ln=Sm, Eu, Gd, Tb)

A new type of lanthanide complex with a derivative of β-diketone and phenanthroline, LnPhβ3·Phen [where Phβ = CCl3–C(O)–N–P(O)–(OCH3)2; Phen = 1,10-phenanthroline, Ln = Sm, Eu, Gd, Tb] was synthesised. The X-ray diffraction analysis of the Sm(III) complex shows that it is in the monoclinic system and P21/c space group. There are two different Sm3+ ions with insignificant differences between the Sm–O, –N distances (0.005 A) and a CN = 8. Absorption, emission and emission excitation spectra at 293, 77 and 4.2 K were used to characterise the title compounds in the solid state and in solution. The luminescence spectra at 77 K for the Eu analogue are complex and two components in the 5D0 → 7F0 transition show that Eu3+ ions reside in two symmetry sites. The spectroscopic results correspond well to the crystal structure of the SmPhβ3·Phen compound and confirm that the Sm3+, Eu3+ and Tb3+ monocrystals are isostructural. Efficient energy transfer sensitises the interion emission from 5D4 or 5D0 levels of Tb(III) and Eu(III) after ligand band excitation. Based on the splitting of the levels observed at 4.2 K in the single crystal spectra of Tb and Eu, as well as the absorption, phosphorescence and excitation spectra, energy level diagrams are proposed. The mechanism of energy transfer and excited state dynamics are discussed. Strong vibronic coupling was observed mainly in the 7F0 → 5D2 electronic transition. The IR spectra were used to analyse the vibronic components. Analysis of the emission spectra of a Eu3+-doped silica sol-gel sample was made and compared to those for the title monocrystals. The total spectral characteristics of the materials permits an evaluation of their potential applicability.

Spectroscopic characterization of lanthanide complexes with N,N′-tetraethyl-N′′-benzoylphosphoryltriamide. Crystal structure of tris(N,N′-tetraethyl-N′′-benzoylphosphoryltriamide) cerium(III) trinitrate complex

Abstract A new range of lanthanide compounds of the formula Ln(HL)3(NO3)3, where Ln=La, CeNd, SmLu, Y; HL=C6H5C(O)N(H)P(O)[N(CH2CH3)2]2N,N′tetraethylN′′-benzoylphosphoryltriamide have been prepared and characterized by means of IR, 1H, 31P NMR and UV–Vis spectroscopies. The compounds are isomorphous according to X-ray powder diffraction studies. The crystal and molecular structure of Ce(HL)3(NO3)3 has been determined by X-ray diffraction studies. The complex has a molecular structure. The monodentate neutral phosphoryltriamide ligands are coordinated to the metal ion via phosphoryl oxygen atom. The coordination polyhedron of Ce is a tricapped trigonal prism, CN=9 [6O(NO3−)+3O(PO)]. By UV–Vis spectroscopy it was shown that in acetonitrile solution the neodymium complex with molar ratio 1:3 (Nd3+:HL) exists (stability constant=2.56).

Novel tetranuclear cubane-like Co(II) complexes involving chelate phosphoramide ligands

Abstract Interaction of cobalt(II) ions and sodium carbacylamidophosphates Na(L) (HL=PhC(O)NHP(O)(NR2)2; where NR2 are morpholyl, HL1; NMe2, HL2; NEt2, HL3) in methanol solution afforded polynuclear alkoxo complexes [Co4{L1}3(OCH3)4(OH)(H2O)5·3H2O] 1 and [Co4{L}4(OCH3)4(CH3OH)4] (L=L2 2, L3 3). Data of spectral and TGA studies are presented. Coordination compounds 1 and 3 have been characterized by means of X-ray diffraction. Both the structures consist of tetranuclear cubane alkoxo clusters with methoxide ions bridging three metal centers (CoO 2.068(3)–2.093(4) A) and phosphorylic ligands coordinated in a bidentatechelate fashion via the carbonyl oxygen atoms (CoO 1: 2.050(2); 3: 2.031(4) A) and the phosphoryl groups (2.093(2) and 2.106(4) A). Isolation of these cubane alkoxo complexes is an important proof for close resemblance in behavior of carbacylamidophosphate systems and β-diketonates towards transition metal ions.

Metal carbacylamidophosphates: ability of coordination patterns to di- and polymerization

Abstract Cobalt(II), nickel(II) and copper(II) complexes with carbacylamidophosphate ligands {Cl 3 C(O)NP(O)R 2 } − (R=OMe, NEt 2 , NHCH 2 Ph, N -morpholyl) were characterized by means of X-ray diffraction, IR, UV–Vis spectroscopy and thermal analysis. The organic ligands were coordinated via oxygen atoms of phosphoryl and carbonyl groups forming six membered chelate cycles. The molecular units M{L} 2 reveal ability for self-association and readily yield different di- and polymeric motifs either by μ 2 -phosphorylic bridges, donor atoms of the morpholine substitute or employing an additional bridging ligand. Cobalt and nickel solvates [M{L} 2 (Pr i OH)] 2 exist as characteristic dimers sustained by phosphoryl bridges between octahedral metal atoms, while copper complexes aggregate through self-complementary CuO interactions with a morpholine substitute forming one-dimensional chains [Cu{L} 2 ] n or dimers [Cu{L} 2 (Pr i OH)] 2 involving terminal 2-propanol ligands. The configuration of binding sites for [Cu{L} 2 ] (R= N -morpholyl) favors the densest pairwise association of the molecules with CuO (morpholine) at approximately 2.55 A.

Correlation between spectroscopic characteristics and structure of lanthanide phosphoro-azo derivatives of β-diketones

Two types of lanthanide (Nd, Eu, Pr) compounds of formulae: Ln(HX) 3 Cl 3 (1), Ln(HX) 3 (NO 3 ) 3 (2) [where HX=CCl 3 CO-NH-PO(NEt 2 ) 2 ] with the same ligand type but with different coordination numbers (as a consequence of different site symmetries) were obtained. X-ray data indicate the formation of octahedral complexes of (1), strongly distorted into trigonal symmetry, the strongest distortion observed for europium single crystals. On the other hand, the second type of crystals creates intermediate coordination polyhedra with low symmetry; anisotropy of intensities of 4 I 9/2 → 4 G 5/2 , 2 G 7/2 transition of Nd crystal well confirms the above structure. High resolution absorption spectra of single crystals of the title compounds were recorded at different temperatures from 293 to 4.2 K. Splitting of levels was determined. Intensities of f-f transitions were calculated and changes of their oscillator strengths, in the region of hypersensitive transitions, for the series Pr, Nd, Eu crystals were related to stronger distortion of the symmetry with a decrease of the ionic radius. Oscillator strength values and Judd-Ofelt parameters were calculated and compared to the respective data reported earlier. Analysis of the electronic components in low temperature spectra point on the D 3 site in (1) and most probably C 2v in (2). Electron-phonon coupling was observed in low temperature spectra and its probabilities was analysed for two types of compounds with different symmetries. Vibronic components were related to the internal ligand modes and to the localised Ln-L x modes.

Contribution of Energy Transfer from the Singlet State to the Sensitization of Eu3+ and Tb3+ Luminescence by Sulfonylamidophosphates

A series of stable lanthanide complexes Na[Ln(L)4 ] (Ln=La3+ , Eu3+ , Gd3+ , Tb3+ , with L=dimethyl(4-methylphenylsulfonyl)amidophosphate and dimethyl-2-naphthylsulfonylamidophosphate) were synthesized. The compounds were characterized by single-crystal X-ray diffraction, IR, absorption, and emission spectroscopy at 293 and 77 K. In contrast to the usual and well-known dominant role of the ligand triplet state in intramolecular energy transfer processes in Ln complexes, in this particular new class of Ln compounds with sulphonylamidophosphate ligands, strong experimental and detailed theoretical evidence suggest a dominant role is played by the ligand first excited singlet state. The importance of the role played by the 7 F5 level in the case of the Tb3+ compound in this process is shown. The theoretical approach for the energy transfer rates was successfully applied to the rationalization of the experimental data. The higher-lying excited levels of Eu (5 DJ , 5 LJ , 5 GJ ) and Tb (5 DJ , 5 GJ , 5 LJ , 5 HJ , 5 FJ , 5 IJ ) were included in the calculations for the first time. Both the multipolar and exchange mechanisms were taken into account. The experimental intensity parameters (Ωλ ), emission lifetimes (τ), radiative (Arad ) and non-radiative (Anrad ) decay rates, and quantum yields (theoretical and experimental) were determined and are discussed in detail.

Synthesis and spectroscopic characteristics of a new class of lanthanide compounds of formulae Ln(HX)3(NO3)3 and Ln(HX)3Cl3

Two series of the lanthanide (Eu, Pr) compounds of the formulae Ln(HX)3Cl3 (1); Ln(HX)3(NO3)3 (2) [where HX=CCl3CO–NH–PO(NEt2)2] with C.N.=6 and 9 were obtained in the form of monocrystals. The spectroscopic properties of these compounds were investigated at 293, 77 and 4.2 K and the results related to their structures. Correlation was made with the spectroscopic data and structure of the Eu and Nd respective chelates. Essential differences were found in coordination mode of ligand molecules in those systems. Intensity analysis of electronic transitions, electron–phonon coupling, as well as splitting and energies of electronic levels were used as tests of metal bonding in the systems under investigation. The electronic f–f transitions of praseodymium (1, 2) compounds show drastic differences in oscillator strength values, pointing thus at substantial differences in symmetry of the metal centre. Judd–Ofelt parameters were calculated with low errors of estimation. The relatively strong vibronic lines appear at displacement frequencies, corresponding to both ligand and Ln–Ln localised vibrational modes.

Dinuclear 3D metal complexes based on a carbacylamidophosphate ligand: redetermination of the ligand crystal structure

Dinuclear Ni(II), Co(II) and Zn(II) complexes of general formula