Neyko Stoyanov

Excited state intramolecular proton transfer in 2-acetylindan-1,3-dione

Abstract Results on the absorption and luminescence properties of 2-acetylindan-1,3-dione in different solvents are reported. Evidence suggesting intramolecular proton transfer in the excited singlet state is presented. All possible tautomeric forms are studied by means of the AM1 method in both the ground and the first excited singlet state. On the basis of the results obtained the tautomers involved in the photocycle are proposed.

Aminoderivatives of cycloalkanespirohydantoins: synthesis and biological activity

3-Aminocycloalkanespiro-5-hydantoins were synthesized and their biological activity was studied. In contrast to hydantoins, these compounds failed to induce either anticonvulsive effects in the central nervous system or inhibitory effects on cholinergic contractions in the enteric nervous system. However, they exerted well pronounced, atropinsensitive, contractile effects on the guinea-pig ileum longitudinal muscle preparations. Structure-activity relationships established allow the assumption that: (i) the reduction of the ring size in the molecule of the spirohydantoins leads to an increase in the potency of the respective analogue to induce contractile effect; (ii) the introduction of -NH2 in position 3 increases the ability of all the compounds studied to exert contractions; (iii) the enlargement of the ring leads to: (1) an increase of the degree of desensitization of the preparations; and (2) a decrease (except 1a) of the potency of the analogues to exert contractile effects.

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.

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.

Copper(II) Complexes of Spirohydantoins. Synthesis, Quantum-Chemical, and Spectroscopic Study

A series of new Cu(II) complexes with important physiologically active cycloalkane-5-spirohydantoines are synthesized reacting as a result of CuCl2 · 2H2O interaction with the ligands in alkaline water medium. Their structures were studied using spectroscopic (IR and EPR) methods. For comparison, ab initio calculations of the structure and IR spectra of the corresponding Cu(II) complexes were also performed. It was proven that with cyclopentane-5-spirohydantoins, distorted (flattened) tetrahedral structure is realized Cu(L−H)2(H2O)2, while with the higher cycloalkane-5-spirohydantoins linear Cu(II) complexes of the type CuL−H(OH) are formed.

Ab initio quantum chemical and NMR study of the symmetric monooximes of 1,2,3-phenalenetrione and 1,2,3-indantrione

Abstract The possibility for nitroso-oxime tautomerism in symmetric monooximes of 1,2,3-phenalenetrione and 1,2,3-indantrione is studied by means of ab initio quantum chemical methods and NMR spectroscopy. For both compounds, ab initio calculations with different basis sets predict the oxime tautomer as most stable in agreement with the 1 H- and 13 C-NMR results in CDCl 3 and DMSO- d 6 solutions. A coalescence of the signals for the carbon atoms from carbonyl groups of 1,2,3-phenalenetrione monooxime in DMSO- d 6 solution at temperature 360 K is observed. This coalescence may be attributed to rotation of the hydrogen atom from the hydroxyl group around the NO bond. The rotational transition structures for both compounds at different computational levels were located in the gas phase and in solution.

Structure of six- and seven-membered cyclic- β-diketones and their metal(II) complexes

Abstract Two new copper(II) complexes with physiologically active ligands containing both pyridine ring and cyclic β-diketones with different ring members were obtained with the metal to ligand ratio 1:2. The structure and coordination mode of both complexes were studied using IR and EPR methods. The AM1 method was applied for calculating the structure of 5, 7-dioxo-6-(2-pyridyl)-6, 7-dihydro-5H-dibenzo (a, c)cyclohepteneand its Zn II complex. It is shown that the structure of both complexes is a tetragonal one and the coordination is realized via the hydroxy O and N of the pyridine ring.

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.

A complete 1H and 13C NMR data assignment for 3-phenylmethylene-1H,3H-naphtho-[1,8-c,d]-pyran-1-one.

Complete assignments of the 1H and 13C NMR chemical shifts for 3-phenylmethylene-1H,3H-naphtho-[1,8-c,d]-pyran-1-one were done by means of one- and two-dimensional NMR techniques, including 1H-(1)H COSY, HMQC and HMBC spectra. Ab initio quantum chemistry calculations and a shift prediction by an incremental method provided values close to the proposed assignments. All mid-IR spectral bands are given as reference data. The DRIFT FTIR, ATR FTIR and Raman spectra are given as a Supplementary data in JCAMP-DX format, version 4.24. In addition, a method of compounds synthesis, that has the product yield higher as compared to already known data in the literature, is given.

FT-IR Spectra of Enol-esters of 2-Aryl-2,3-dihydrophenalene-1,3-diones

The FT-IR spectra of new enol-esters of 2-aryl-2,3-dihydrophenalene 1,3-diones have been measured. The influence of the structure of the compounds on the position of the C=O and OC=O stretching bands is discussed. The available experimental data from the FT-IR spectra suggest the presence of bipolar structures due to the ester resonance.