Anife Ahmedova

1H, 13C MAS NMR and DFT GIAO study of quercetin and its complex with Al(III) in solid state

Quercetin (Q) as a pentahydroxy flavonoid, has three possible chelating sites competing in complexation processes. (1)H and (13)C MAS NMR spectra were recorded for solid quercetin and its Al(III) complex (AlQ). (1)H MAS spectrum of quercetin shows a broad resonance at ca. 12 ppm that confirms the existence of intramolecular C5-OH … O=C4 hydrogen bond. Such a signal is absent in the spectrum of AlQ, which is in accordance with other spectroscopic data and the suggested model for the solid-state structure of the complex. DFT GIAO calculations were used to verify the experimental (13)C CPMAS NMR data and to suggest the best model structure for the complex AlQ. The calculated shielding constants for different conformers of isolated quercetin molecules, quercetin trimer as taken from the X-ray data, and different model structures for possible Al(III) complexes were compared with the (13)C CPMAS NMR experimental values. The results demonstrate the importance of intermolecular interactions when dealing with structures in solid state and the successful application of the combined DFT GIAO and (13)C CPMAS NMR approach. All data confirm that the chelating site of Q in the solid complex AlQ involves the deprotonated C5-OH and the C4=O groups at ring C, in contrast to the available studies performed in solution.

Anticancer Potencies of Pt(II) - and Pd(II)-linked M2L4 Coordination Capsules with Improved Selectivity.

Pt(II) - and Pd(II)-linked M2 L4 coordination capsules, providing a confined cavity encircled by polyaromatic frameworks, exhibit anticancer activities superior to cisplatin against two types of leukemic cells (HL-60 and SKW-3) and pronounced toxicity against cisplatin-resistant cells (HL-60/CDDP). Notably, the cytotoxic selectivities of the Pt(II) and Pd(II) capsules toward cancerous cells are up to 5.3-fold higher than that of cisplatin, as estimated through the non-malignant/malignant-cells toxicity ratio employing normal kidney cells (HEK-293). In addition, the anticancer activity of the coordination capsules can be easily altered upon encapsulation of organic guest molecules.

2‐Acetylindan‐1,3‐dione and its Cu2+ and Zn2+ complexes as promising sunscreen agents

In continuation of a previous spectroscopic and quantum chemical study on 2‐acetylindan‐1,3‐dione (2AID), the spectral properties and photostability of 2AID and its Cu2+ and Zn2+ complexes in different solvents are reported. Comparison is made with the photostability of two commercially available sunscreens: benzophenone‐3 and octylmethoxycinnamate. 2AID exhibits a higher photostability, high molar absorption coefficient (42 000 m−1 cm−1) at λmax and broad‐spectrum UV‐protection properties.

Quantum chemical and spectroscopic study of the structure of 2-acetylindan-1,3-dione complexes with metal(II) ions

Abstract A series of M(II) (M=Cu, Zn, Cd, Pb) complexes with the physiologically active 2-acetylindan-1,3-dione were synthesized. All complexes were obtained with the metal to ligand ratio 1:2. The presence of two water molecules in the inner coordination sphere of the Zn(II) and Cd(II) complexes was proven. The structure and coordination mode of the newly synthesized Cd(II) and Pb(II) complexes were investigated using NMR ( 13 C CPMAS and 13 C NMR in DMF-d 7 solution) method. Semi-empirical (PM3) and ab initio (ECP-31G) calculations of the structure and IR spectra of the free ligand and corresponding metal(II) complexes were performed. It is shown that the structure of the Pb(II) complex differs significantly from the distorted tetrahedral structure of the Cu(II), Zn(II) and Cd(II) complexes.

Reaction of 2-acetyl-indane-1,3-dione with aniline - Schiff base or enamine?

The structure of the product of the condensation reaction between 2-acetylindan-1,3-dione and aniline has been investigated in the gas phase, solution and solid state using a combination of quantum-chemical calculations, NMR and IR spectroscopies, and X-ray crystallography. Energetics of both isomers and all tautomers of the product of the reaction are predicted at HF/321G//HF/3-21G and HF/6-31G**//HF/3-21G levels. Geometric optimizations at HF/6-31G** level are also performed for favorable tautomers. Quantum-chemical calculations indicate that the enamine isomer, 2-[1-( N-phenylamino)-1-ethylidene]indane-1,3-dione is favored. This is confirmed by 13 C NMR spectroscopy in non-polar and polar solvents, and in the solid state by X-ray crystallography. q 2003 Elsevier Science B.V. All rights reserved.

Synthesis, characterization and spectroscopic properties of some 2-substituted 1,3-indandiones and their metal complexes

New 2-acyl-1,3-indandione derivatives, compounds 1–4, were obtained by condensation of 2-acetyl-1,3-indandione with benzaldehyde, thiophene-2-aldehyde, thiophene-3-aldehyde and furane-2-aldehyde, respectively. The structures of the newly synthesized 2-substituted 1,3-indandiones were characterized by means of spectroscopic methods (FT-IR, 1H and 13C NMR, UV-Vis and MS). Based on the obtained results it is suggested that the compounds exist in the exocyclic enolic form. Mass spectral fragmentation paths are also proposed. In order to verify the possibility for tautomerization processes of the newly synthesized compounds their absorption spectra were recorded in various solvents. Furthermore, the complexation properties of the compounds with metal(II) ions were also studied. A series of non-charged complexes with Cu(II), Cd(II), Zn(II), Co(II) and Ni(II) was isolated and analyzed by elemental analyses and IR. The paramagnetic Cu(II) complexes were studied by EPR and distorted, flattened tetrahedral structures are predicted. The other metal complexes show the presence of water molecules, most probably coordinated to the metal ion, thus forming octahedral geometry. Ultimately, the studied properties of the newly synthesized compounds, 1–4, suggest that they may find application as extracting agents for metal ions, rather than as optical sensors.

X-ray structure and magnetochemical study on a Co(II) complex of 2-acetyl-1,3-indandione

An X-ray structure of a Co(II) complex of bidentate chelating 2-acetyl-1,3-indandione (2AID) is reported–Co(2AID)2(H2O)2 · 2H2O. The compound crystallizes in the monoclinic space group P21/n with four molecules per unit cell. The molecular structure shows distorted octahedral geometry of the metal center. The complex is characterized by EPR and magnetic measurements, which show high-spin electronic structure for the metal ion.

High frequency EPR of a copper(II) trimer: experiment time scale effects in EPR spectroscopy

High-frequency (190 GHz) EPR spectra are reported, that were recorded on an exchange coupled, trimeric copper cluster, octachlorodiadeniniumtricopper(II). The lines in the rhombic spectra shift as a function of temperature. This can be traced to the presence of two close lying spin doublet states, with different g tensors, that interconvert quite rapidly. Therefore, the lines observed in the spectrum have the Boltzmann weighted average of the two g values. The interesting observation is that signals due to the excited spin doublet are observed. This means that the interconversion rate is of the same order of magnitude as the Electron Paramagnetic Resonance experiment. Previous experiments at X-band frequency (9 GHz) could only ascertain that the interconversion rate was faster than that frequency.

Structure and properties of a series of 2-cinnamoyl-1,3-indandiones and their metal complexes

A series of seven 2-cinnamoyl-1,3-indandiones and their metal(II) complexes were synthesized and characterized by means of spectroscopic (IR, NMR, electron absorption and emission spectroscopy) and/or single-crystal X-ray diffraction methods. The optical spectra of the organic compounds show very strong absorption in the visible region and weak fluorescence with moderate to strong Stokes shift. The effect of concentration, water addition and metal ion complexation on the optical properties was also studied. In search of potential practical application, the complexation of 2-cinnamoyl-1,3-indandiones with metal(II) ions was investigated. A series of non-charged complexes with Cu(II), Cd(II), Zn(II), Co(II) and Ni(II) was isolated and analyzed by elemental analyses and IR. Most of the complexes show presence of water molecules, most probably coordinated to the metal ion, thus forming octahedral geometry. For the paramagnetic Cu(II) complexes a distorted, flattened tetrahedral structure is proposed, basing on the EPR data. The optical properties of the metal complexes, however, do not differ appreciably from those of the free ligands.

X-Ray and EPR study on copper(II) complexes with an enamine ligand

The enamine (HEAID) obtained from aniline and 2-acetyl-1,3-indandione (2AID) behaves as a bidentate ligand in coordination with copper (II) ion. Two types of crystals, apparently different in shape, were isolated and studied by single-crystal X-ray diffraction. The X-ray data for the brown rhombic crystals of compound 1 shows a mononuclear complex of Cu(II) coordinated with two EAID-anions, Cu(EAID)2. The X-ray data for the green crystals of compound 2 shows a dinuclear Cu(II) complex with two OH− groups acting as bridging ligands, [Cu2(μ-OH)2(EAID)2]. In both cases the ligand coordinates after deprotonation of the amine group.