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Dive into the research topics where Mikelis V. Veidis is active.

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Featured researches published by Mikelis V. Veidis.


CrystEngComm | 2009

Nicotinamide fumaric acid supramolecular cocrystals: diversity of stoichiometry

Liana Orola; Mikelis V. Veidis

Synthesis of nicotinamide and fumaric acid supramolecular cocrystals with 1 : 1 and 2 : 1 amide to acid stoichiometries results in the formation of an amide–acid heterosynthon (1 : 1 stoichiometry) and an amide–amide homosynthon (2 : 1 stoichiometry) and different conformations of the fumaric acid moieties.


New Journal of Chemistry | 2013

Spontaneous cocrystal hydrate formation in the solid state: crystal structure aspects and kinetics

Inese Sarcevica; Liana Orola; Sergey Belyakov; Mikelis V. Veidis

Kinetics of anhydrous cocrystal hydration and that of cocrystal monohydrate formation from starting compounds in the solid state are studied as a function of RH and time. The propensity of the anhydrate to hydration is related to the crystal structures of anhydrous and hydrated forms.


International Journal of Pharmaceutics | 2012

The effect of pH on polymorph formation of the pharmaceutically active compound tianeptine

Liana Orola; Mikelis V. Veidis; Inese Sarcevica; Andris Actins; Sergey Belyakov; Aleksandrs Platonenko

The anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified.


Acta Crystallographica Section E-structure Reports Online | 2008

N-(2,6-Dimethyl­anilino)-5,6-dihydro-4H-1,3-thia­zin-3-ium chloride monohydrate

Mikelis V. Veidis; Liana Orola; Reinis Arajs

In the title compound, alternatively called xylazine hydrochloride monohydrate, C12H17N2S+·Cl−·H2O, the six-membered thiazine ring is in a half-chair conformation. In the crystal structure, six component centrosymmetric clusters are formed via intermolecular O—H⋯Cl, N—H⋯O and N—H⋯Cl hydrogen bonds involving xylazine cations, chloride anions and water molecules.


CrystEngComm | 2012

The conformation of pyrogallol as a result of cocrystallization with N-heterocyclic bases

Mikelis V. Veidis; Liana Orola; Ilpo Mutikainen; Inese Sarcevica

Structural analysis of the supramolecular cocrystals formed by pyrogallol with acridine, 4,4′-bipyridine, and 1,10-phenanthroline shows that the studied cocrystals are assembled via the hydroxyl–pyridine heterosynthon. In the crystal and molecular structures of these cocrystals in order to form the maximum number of hydrogen bonds, taking into consideration steric effects, the pyrogallol moiety in the supramolecular arrangement has the following conformations: with acridine - syn1, 4,4′-bipyridine - anti, and 1,10-phenanthroline - syn2. Discrete supramolecular complexes are formed by acridine–pyrogallol and the 1,10-phenanthroline–pyrogallol polymorph I. The 1,10-phenanthroline–pyrogallol polymorph II and the 4,4′-bipyridine–pyrogallol trihydrate form extended hydrogen bonded chains.


Acta Crystallographica Section E-structure Reports Online | 2010

Bis(N,N′-diphenyl­benzamidinium) fumarate

Liana Orola; Mikelis V. Veidis

The crystal structure of the title compound, 2C19H17N2 +·C4H2O4 2−, consists of centrosymmetric trimers built up of two crystallographically independent N,N′-diphenylbenzamidinium cations and one fumarate dianion, which is located on a centre of inversion. The components of the trimers are linked by N—H⋯O hydrogen bonding. In the cation, the outer rings make dihedral angles of 53.66 (5) and 78.38 (5)° with the central ring. The two outer rings make a dihdral angle of 81.49 (5)°.


Acta Crystallographica Section E-structure Reports Online | 2008

Dipotassium 4,4'-(hexane-3,4-di-yl)bis-(benzene-sulfonate) dihydrate.

Liana Orola; Mikelis V. Veidis; Sergey Belyakov; Andris Actins

The anion of the title compound, also called sygethin dihydrate, 2K+·C18H20O6S2 2−·2H2O, has crystallographic inversion symmetry. The K+ cation is surrounded by eight O atoms in a distorted cubic coordination geometry, forming extended K—O—S networks. There are also O—H⋯O hydrogen bonds.


Crystal Growth & Design | 2013

Crystal and Molecular Structure and Stability of Isoniazid Cocrystals with Selected Carboxylic Acids

Inese Sarcevica; Liana Orola; Mikelis V. Veidis; Anton Podjava; Sergey Belyakov


Crystal Growth & Design | 2011

Neutral and Ionic Supramolecular Complexes of Phenanthridine and Some Common Dicarboxylic Acids: Hydrogen Bond and Melting Point Considerations

Liana Orola; Mikelis V. Veidis; Ilpo Mutikainen; Inese Sarcevica


Journal of Molecular Structure | 2014

Conformation of the umifenovir cation in the molecular and crystal structures of four carboxylic acid salts

Liana Orola; Inese Sarcevica; Artis Kons; Andris Actins; Mikelis V. Veidis

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Sergey Belyakov

Riga Technical University

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