
Rositsa Petrova NikolovaBulgarian Academy of Sciences | BAS · Ivan Kostov Institute for Mineralogy and Crystallography
Rositsa Petrova Nikolova
PhD
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236
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Introduction
Rosica P Nikolova currently works at the Ivan Kostov Institute for Mineralogy and Crystallography, Bulgarian Academy of Sciences. Rosica does research in Mineralogy, Geochemistry and Organic Chemistry. Their current project is 'Crystal structure of DNA G-Quadruplexes'.
Additional affiliations
September 1989 - June 2016
Education
September 1985 - June 1989
Publications
Publications (236)
First find of alpersite for Bulgaria is reported. The specimens have been collected from an abandoned exploration drift in the Lozen ore field, Eastern Rhodopes. The studied crystals have prismatic habit and typical for the mineral pale blue color. XRF, XRD, SEM-EDS and DSC-TG analyses have been used to characterize the samples. The obtained crysta...
This paper poses a major question regarding the choice of space group for scapolite mineral group members. An artificial boundary is typically drawn between space groups I4/m and P4 2 /n when solving the structures of scapolites within the marialite-meionite series. The authors debate if solving the crystal structure in lower symmetries is justifie...
A R T I C L E I N F O Keywords: Tunable photoluminescence White light emitter 3D-2D-3D transformation Rare-earth silicate Metastable phase A B S T R A C T The synthesis of zeolites and porous heteropolyhedral silicates is usually accompanied by crystal phase transformations. Typically, this process is irreversible and characterized by a conversion...
Detailed studies of the Li4GeО4-Li2CaGeО4 system by solid-phase syntheses of various compositions from pure Li4GeО4 to pure Li2CaGeО4 in the temperature range from 25 to 1125 °C is investigated for a first time. Solid state synthesis powders are characterized by X-ray and DSC/TG methods. Concentration and temperature two-phase regions of Li4GeО4 an...
Citation: Nikolova, R.; Kostov-Kytin, V.; Petrova, N.; Kosev, K.; Titorenkova, R.; Velyanova, G. New Data on Crystal Phases in the System Abstract: Urea complexes of magnesium sulfate have been intensively studied due to their application in many areas of life, including agricultural chemistry, pharmacy, medicine, etc. The aim of this study is to a...
A theoretical model of the crystal structure of the newly obtained compound Zn4(OH)6SO4·2–2.25H2O based on the compilation of the crystal–chemical properties of two known zinc-hydroxy-sulfate phases—mineral namuwite and hemihydrate—is proposed. The single XRD data confirmed the model and determined the structure, with a trigonal symmetry SG of P-3,...
Three new molecular complexes (phen)3(2-amino-Bz)2(H+)(BF4−)·3H2O 5, (phen)3(2-amino-5(6)-methyl-Bz)2(H+)(BF4−)·H2O 6, and (phen)(1-methyl-2-amino-Bz)(H+)(BF4−) 7, were prepared by self-assembly of 1,10-phenanthroline (phen) and various substituted 2-aminobenzimidazoles. Confirmation of their structures was established through spectroscopic methods...
In the present work, the methods for reducing the losses of bound nitrogen when applying fertilizer
compositions to the soil are presented. In this regard a promising preparation has been developed which is a complex
of urea with magnesium sulfate, namely hexaureato magnesium sulfate hemihydrate, [Mg ((H2N)2CO)6] SO4. 1/2
H2O. The preparation can b...
A suite of sulphates from a locality in Lozen ore field in the Eastern Rhodopes has been characterized by chemical analyses and X-ray diffraction. Three mineral species have been identified: epsomite (MgSO4), pickeringite (MgAl2(SO4)4•22H2O) and alunogen (Al2(SO4)3•17H2O). An attempt was made to characterize the phase transformations that occur upo...
The current study presents results of crystal chemical studies of epidote samples from two Central Rhodope localities. Based on the obtained crystal chemical information, the nomenclature of the investigated species has been justified within the IMA-recommended nomenclature of epidote-group minerals. A comparative study has also been accomplished,...
The paper provides new insight on the choice of correct space group for description of scapolite crystal structures, with a view of the preferred positions by Si and Al ions and their framework ordering. Samples of scapolite from a skarn zone around Urdini lakes, Northwestern Rila have been analysed with SEM-EDS and single crystal X-ray diffraction...
Samples of scapolite from the marble quarry from the Samurski Dol locality, situated nearby Chepelare, Central Rhodopes, Bulgaria have been subjected to chemical analyses and single crystal X-ray diffraction studies. The obtained values for the meionite component (Me) range between 70 and 75. The crystal structure of the studied sample has been sol...
Structural characteristics of serpierite samples from Zvezdel, Bulgaria, and Lavrion, Greece, are reported. The thermal behaviour of serpierite from Lavrion is discussed. The chemical composition of the studied samples is analysed by energy-dispersive spectroscopy (EDS) and confirmed by single-crystal structure refinements. The obtained chemical fo...
Powder samples of Li2CaGeO4, Ca2GeO4 and Ca5Ge3O11 doped by 0.5, 1, 2, 3, 4 and 5 at% Eu3+ relative to the Ca2+, were prepared by conventional solid state synthesis technique. XRD analyses confirm obtaining of the pure phases at all dopant concentrations. In parallel, single crystals of the three compounds with the experimentally found optimal Eu3+...
Three Mg(II) perrhenate complexes were synthesized in aqueous solution and the crystal structures of neutral Mg(H2O)2(ReO4)2 (1) and two novel ionic complexes with urea (U, OC(NH2)2), [Mg(H2O)2(U)4](ReO4)2 (2) and [Mg(U)6](ReO4)2 (3) were determined by single crystal X-ray diffraction. The compounds were examined by DTA-TG-MS analysis, FT-infrared...
This work reports the synthesis and characterization of novel zeolite-like indium silicate MS-2 (Minho-Sofia, solid number 2). The structure of this material is analogous to that of the mineral imandrite (Na6Ca1.5FeSi6O18), with In instead of Fe in the octahedral position. MS-2 is the first structurally confirmed indium silicate prepared under mild...
Pseudo-ternary system Li2O·MoO3–CaO-GeO2 was investigated. The concentration and temperature regions of crystallization of a new compound Li2CaGe6O14 were experimentally established. Single crystals from this compound were grown and it structure was solved by single crystal XRD investigation. The chemical composition was confirmed by electron probe...
Here, we describe the synthesis, characterization, and biological activities of a series of 26 new styryl-2(3H)-benzothiazolone analogs of combretastatin-A4 (CA-4). The cytotoxic activities of these compounds were tested in several cell lines (EA.hy926, A549, BEAS-2B, MDA-MB-231, HT-29, MCF-7, and MCF-10A), and the relations between structure and c...
Here, we describe the synthesis, characterization, and biological activities of a series of 26 new styryl-2(3H)-benzothiazolone analogs of combretastatin-A4 (CA-4). The cytotoxic activities of these compounds were tested in several cell lines (EA.hy926, A549, BEAS-2B, MDA-MB-231, HT-29, MCF-7, and MCF-10A), and the relations between structure and c...
Small-pore iron silicate MS-1 (Minho-Sofia, solid number 1) with a 3D porous system, an analogue of the rare mineral imandrite, has been synthesized and characterized. This material is the lowest framework density iron silicate, one of the most siliceous (Si/Fe = 6) iron silicates, the first iron cyclosilicate achieved at hydrothermal conditions, a...
This work deals with Cu-modified 1DTiO2 microrods (MRs) and their surface properties. The pristine lyophilized precursor Cu_1DTiO2, prepared by an environmentally friendly cryo-lyophilization method, was further annealed in the temperature interval from 500 to 950 °C. The microstructure of all samples was characterized by electron microscopy (SEM/E...
A series of acylpyrazolones possessing methylene bridged heterocyclic unit in the acyl fragment is synthesized and characterized in solution and solid state. It is found that the products exist in...
Morphology, chemical composition, crystal structure and IR spectroscopy characteristics of a first find of libethenite, Cu 2 (PO 4)(OH), in the Sarneshko Kladenche deposit, Rosen ore field, Eastern Srednogorie, were studied. The mineral is presented by 0.8-1.4 mm long-prismatic crystals with {100}, {010}, {110}, {210}, and {011} crystallographic fo...
The utility of deoxy-isoequilenine synthesized from estrone as valuable 2-naphthol analogue is demonstrated in the three components Betti-condensation. A simple, efficient and green procedure for the synthesis of aminobenzylnaphthol analogues (so-called Betti bases) has been realized highly diastereoselectively by using (S)-phenylethylamine and 1-...
The crystal structures of newly obtained [Mg(OC(NH2)2)2(H2O)4]I2 (tetraaqua bis (urea-O) magnesium diiodide), [Mg(OC(NH2)2)4(H2O)2]I2 (diaqua tetra(urea-O) magnesium diiodide) and [Mg(OC(NH2)2)6]I2 . 4OC(NH2)2 (hexa(urea-O) magnesium diiodide tetraureate) are reported. It is found that the studied compounds crystalize in the same space group P21/c...
New investigations on the columbite from Vishteritsa locality, Western Rhodopes have been performed in order to obtain precise data on its chemical composition and thus to determine its particular mineral species type in the light of the changes in the nomenclature and classification of the columbite group undertaken by IMA since 2007. The capabili...
A series of hydrothermal syntheses in the system Na 2 O-SnO 2-SiO 2-H 2 O at 200 • C without organic additives in the reaction mixture led to preparation of four phases one of which has as a structural analogue the mineral epistolite. Single Crystal and Powder X-ray diffraction (XRD), thermogravi-metric/differential thermal analysis (TG/DTA), scann...
Effect of La Additive on the Morphology and Photocatalytic Perfomance of 2D TiO2 Nanosheets: Degradation of 4 Chlorophenol - Volume 25 Supplement - Snejana Bakardjieva, Radek Fajgar, Victor Y. Zenou, Hana Bibova, Efthalia Chatzisymeon, Rosica Nikolova
Elpidite from the Lovozero alkaline complex, Kola Peninsula, Russia, and Ag-exchanged forms of elpidite from two different localities (Lovozero and Khan Bogdo, Mongolia) were studied by means of single-crystal X-ray diffraction, electron microprobe analysis, thermogravimetry and IR spectroscopy. All studied samples retain the heteropolyhedral frame...
Background:
The accidental discovery of Cisplatin's growth-inhibiting properties a few decades ago led to the resurgence of interest in metal-based chemotherapeutics. A number of well-discussed factors such as severe systemic toxicity and unfavourable physicochemical properties further limit the clinical application of the platinating agents. Grea...
A direct conversion of piperazinyl ethanols into chlorides via a classical O-tosylation protocol is observed. The acceleration of the transformation by the piperazine unit is demonstrated. It is found that the reaction goes via the corresponding O-tosylate, which converts spontaneously into chloride with different rate depending on the substrate st...
In situ time-resolved powder X-ray diffraction technique has been applied to investigate the structural evolution of Zn-exchanged polycrystalline titanosilicate ETS-4 upon heating within the temperature interval from 25 to 375 °C. The facilities of the Rietveld method as implemented in the software package GSAS have been used to control the plau-si...
Microporous titanosilicate Na-K-ETS-4 has been synthesized and subsequently exchanged on Mn 2+. The crystal structures of the as-synthesized and the exchanged forms have been analyzed by single crystal X-ray diffraction at 290 K and 150 K, correspondingly. The elasticity and stability of the titanosilicate framework have been investigated as import...
A series of Betti bases from 4‐(3‐pyridyl)azo‐1‐naphthol dye, possessing flexible methylene or more constrained aryl‐methyne spaced NH‐containing side‐chains, were obtained and characterized. It was shown by NMR spectroscopy that the ligands exist in keto form. The products’ structure was confirmed by single crystal XRD of a selected sample. A stud...
DNA sequences such as 5'-CGTGAATTCACG-3'(S1) and 5'-CGCGAATTCGCG-3'(S2), which are characteristic regions rich in AATT bases, bind many drug forms for treatment of oncology diseases and marker dyes used in fluorescence microscopy. These DNA sequences are also interesting because of the presence of a DNA binding site with the restriction enzyme EcoR...
Alluaudite sulfates are predicted to be high-voltage electrodes for lithium- and sodium-ion batteries. Herein, we provide a first experimental evidence for operation of sodium cobalt-manganese sulfate, Na2+2δ(Co0.63Mn0.37)2-δ(SO4)3 at potentials higher than 4.0 V vs Li/Li+. This fact comes as a result of the reduced cationic deficiency, redox prope...
Five magnesium complexes two of which with tetrafluoroborate anion [U 6 Mg] 2+ .2BF 4-1, [(H 2 O) 6 Mg] 2+ .2BF 4-2, two with chloride anion-[U 6 Mg] 2+ .2Cl-.4U-3, [U 4 Mg(H 2 O) 2 ] 2+ .2Cl-4 and one with nitrate anion-[U 6 Mg] 2+ .2NO 3-5, have been synthesized. Crystals suitable for X-ray diffraction have been obtained by slow evaporation from...
Key words: zeolite microporous material, structural similarity, phase transition. Zirconium containing minerals are scarcely distributed in nature and generally their formation is attributed to hydrothermal alkaline conditions. The most recent statistics of the IMA Commission on New Minerals, Nomenclature and Classification shows that among the zir...
The first finding of fluorwavellite Al2.90(PO4)2(OH)2.[F0.88(OH)0.12]5H2O (+0.10H+) from the Balkan Peninsula was studied by XRD, FTIR, Raman spectroscopy and thermal analysis. The unit cell volume of the sample is comparably smaller than that of the wavellite and fluorwavellite studied so far. The vibrational modes of water molecules and hydroxyl...
Microporous titanosilicate Na-K-ETS-4 has been synthesized and subsequently exchanged on Mn 2+. The crystal structures of the as-synthesized and the exchanged forms have been analyzed by single crystal X-ray diffraction at 290 K and 150 K, correspondingly. The elasticity and stability of the titanosilicate framework have been investigated as import...
A series of twelve novel compounds, analogues of antiviral agent MDL-860 were synthesized and their antiviral activity was evaluated in vitro against enteroviruses poliovirus 1 (PV1), Coxsackieviruses B1 (CVB1) and Coxsackieviruses B3 (CVB3). Compounds 14, 24 and 25 manifested strong antiviral effects against CVB1 and PV1 (SI values of 405 and 118...
Herein is described the synthesis of (+)-camphor derivatives containing sulfonamide groups, ferrocenylmethylidene or arylidene moieties. The obtained derivatives were tested against seven human cancer cells lines, namely BV-173, K-256a, NB-4, A549, H1299, MCF-7, MDA-MB231 and two normal human cell lines HEK293 and HUVEC in order to determine their...
A multi-step methodology for the synthesis of 4-acetyl-2(3H)-benzothiazolone was developed in order to prepare a new biomimetic analogue of benzoxazolone allelochemicals. The compound was prepared from commercially available o-toluidine in 23% overall yield. The structure of 4-acethyl-2(3H)-benzothiazolone was confirmed by NMR spectroscopy and X-ra...
The „sparteine surogate“ (+)-(1R,5S,11аS)-tetrahydrodeoxocytisine is obtained by two known protocols, direct and two-step procedure, and is characterized in solution and solid state as free base, mono-, and bis-hydrochloride. Unambiguous assignment of the proton and carbon NMR spectra of tetrahydrodeoxocytisine is reported for the first time. X-ray...
A new method for the synthesis of 1,3-disubstituted benzimidazole derivatives was developed using aza-Michael addition. The target compounds were synthesized in good yields and purity and tested on isolated hepatocytes for their toxicity and antioxidant activity. The antioxidant properties of the substances with lowest toxicity were evaluated using...
A novel anthracene-derived α-aminophosphonate has been synthesized through a classical addition reaction of dimethyl phosphite to a Schiff base and via a microwave assisted Kabachnik-Fields reaction. The compound has been characterized by elemental analysis, TLC, IR, NMR and fluorescent spectra. The X-ray analysis showed that the compound crystalli...
(Z)-5-(4-Methoxy-3-nitrostyryl)-1,2,3-trimethoxybenzene (2) is the key intermediate for the preparation of several anticancer agents, belonging to the group of aminocombretastatins (AC7739, AVE8062). Synthesis of the title compounds was achieved by a modified Wittig reaction under Boden’s conditions using potassium carbonate as a base and 18-crown-...
The synthesis, IR, NMR and X-ray structure of 2-[(2,3-dihydro-2-oxo-3-benzoxazolyl)methyl]benzoic acid – a potential new drug scaffold are reported. The compound crystallizes in the triclinic P-1 space group with unit cell parameters: a = 6.716(3), b = 7.828(4), c = 13.283(5) Å, α = 78.029(12), β = 81.360(17), γ = 65.7100(10) °, V = 621.0 (4) Å3, M...
The alluaudite-type of structure is of huge research interest as an open matrix ensuring fast alkaline ion mobility, a property that could contribute to the development of novel electrode materials for rechargeable alkaline ion batteries. In this contribution, we provide new data on the formation of well-crystallized sodium manganese sulfates Na2+δ...
The conformational behaviour of 3-methyl-4-(4-methylbenzoyl)-1-phenyl-pyrazol-5-one was studied
using a combination of X-ray diffraction, NMR spectroscopy in solution and solid state, and DFT
calculations in the gas phase. The compound can adopt four different tautomers, determined by the
combination of the keto–enol tautomerism of pyrazolone and t...
Three novel N-(α-bromoacyl)-α-amino esters: methyl 2-(2-bromo-3-methylbutanamido)pentanoate (1), methyl 2-(2-bromo-3-methylbutanamido)-2-phenylacetate (2) and methyl 2-(2-bromo-3-methylbutanamido)-3-phenylpropanoate (3) were synthesized. Single crystal X-ray diffraction data are reported for compounds 1 and 2. The cytotoxicity, anti-inflammatory an...
The efficiency of enantiomeric 1-phenylethylamines and regioisomeric 2- and 4-hydroxynaphthadehydes derived imines as auxiliaries in trans-β-lactam formation via Staudinger cycloaddition was studied. The structures were assigned by 1D and 2D NMR techniques including variable temperature experiments. The influence of the hydroxyl group position on t...