
Kaisa HelttunenUniversity of Jyväskylä | JYU · Department of Chemistry
Kaisa Helttunen
Ph.D.
About
26
Publications
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322
Citations
Introduction
Additional affiliations
April 2016 - May 2016
September 2014 - February 2015
January 2010 - February 2010
University of Applied Sciences Northwestern Switzerland, Basel, Switzerland
Position
- Visiting researcher
Publications
Publications (26)
Conformationally flexible tertiary amine – thiourea−urea catalysts 1 and 2 for the Mannich reaction between imines and malonate esters are efficiently inhibited by quaternary ammonium halides. NMR titrations, isothermal titration calorimetry (ITC) and NOE experiments showed that the catalysts bind chloride and bromide ions with relatively high affi...
Conformationally flexible tertiary amine—thiourea-urea catalysts for the Mannich reaction between imines and malonate esters are efficiently inhibited by quaternary ammonium halides. NMR titrations, isothermal titration calorimetry and NOE experiments showed that the catalysts bind chloride and bromide ions with relatively high affinities (K = 103–...
Calix[4]pyrroles bearing hydroxyl (1) or urea (3) groups attached to the meso-positions with propyl linkers were synthesized as cis- and trans-isomers. The anion binding properties of cis-1 and cis-3 were screened with ion-mobility mass spectrometry, where cis-1 formed complexes with Cl-, Br- and H2PO4-, whereas cis-3 formed complexes with most of...
An aryl-extended calix[4]pyrrole with four meso‑p-hydroxyphenyl substituents was investigated as a host for chloride, acetate, and benzoate anions. Crystal structures of pyridinium and imidazolium chloride complexes were obtained in which chloride ions are hydrogen bonded exo-cavity to the upper rim hydroxyl groups, and the aromatic cations are bou...
The Cover Feature shows conformational switching of a doubly strapped calix[4]pyrrole upon complexation with anions that reminds of the shape change of a Venus flytrap. Artwork by brgfx on Freepik. More information can be found in the Research Article by K. Helttunen.
A calix[4]pyrrole receptor bearing two proximally meso‐meso linking isophthaloyl straps displays open and closed states depending on the calix[4]pyrrole conformation. In the crystal structures and in non‐polar solvent, the calix[4]pyrrole adopts open 1,3‐alternate conformation with straps on the sides. Anion binding triggers a closed state of the r...
The efficient and environmentally sustainable separation process for rare earth elements (REE), especially for adjacent lanthanoids, remains a challenge due to the chemical similarity of REEs. Tetravalent actinoids, thorium, and traces of uranium are also present in concentrates of REEs, making their separation relevant. This study reports six simp...
Does my crystal structure match with the solution conformation? A conformationally flexible resorcinarene macrocycle forms a self‐inclusion complex in the solid state and adopts a similar folded conformation also in solution. The study was performed by using variable temperature (VT) NMR, XRD, and computational methods. For more information, see th...
The synthesis of tetramethoxyresorcinarene podands bearing p‐toluene arms connected by ‐SO3‐ (1) and ‐CH2O‐ (2) linkers is presented herein. In the solid state, the resorcinarene podand 1 forms an intramolecular self‐inclusion complex with the pendant p‐toluene group of a podand arm, whereas the resorcinarene podand 2 does not show self‐inclusion....
The anion‐binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The ¹H NMR spectra of the foldamers in [D6]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable...
Aromatic oligoamide foldamers containing a central pyridine-2,6-dicarbonyl motif are partially preorganized to favor the binding of the fluoride anions. In the solid state the foldamer-fluoride complexes form achiral, polar and chiral crystal structures depending on the chemical structure of the foldamer. One of the six foldamers studied here, a C2...
Resorcinarene bis-thiacrown hosts 1–3 were prepared and crystallized with silver trifluoroacetate yielding one and two dimensional Ag coordination polymers. The complexation of silver in exo-cavity fashion folds the thiacrown bridges inwards transforming the resorcinarene hosts into inverted molecular cups. The silver cations were coordinated to th...
A disulfonamide compound with bulky aromatic side chains was prepared and its properties as a potential building block for foldamers evaluated. Two different solvate crystal forms of the compound were identified and compared to the structures of an analogous oligoamide and related disulfonamides. The disulfonamide is unfolded in one of the solvates...
C-methyl resorcinarene bis-crown-5 (1) with pendant methyl groups at the lower rim was prepared and crystallized in various solvent mixtures with and without selected metal salts. The crystal structures of two polymorphic forms of unsolvated 1 (1-I and 1-II), three solvates (acetonitrile, chloroform and dichloromethane-methanol), and three metal co...
This communication demonstrates the possibility to nucleate and grow different crystalline polymorphic forms of gabapentin (GBP) using, as nucleation templates, Langmuir monolayers of an amphiphilic calixarene at different packing densities.
The interplay of strong and weak hydrogen bonds, dipole–dipole interactions, and aromatic interactions of o- and p-nitroaniline derivatives was studied by combining crystal structure analysis and density functional theory (DFT) calculations. Crystal structures of four 2-nitroaniline derivatives, 2-((2-nitrophenyl)amino)ethyl methanesulfonate (1A),...
The crystal structures and molecular conformations of two foldamer-type oligoamides were analyzed.
One polymorphic form and seven solvates were found for N1,N3-bis(2-benzamidophenyl)benzene-1,3-
dicarboxamide (the benzene variant), and two polymorphic forms and six solvates for N2,N6-bis(2-
benzamidophenyl)pyridine-2,6-dicarboxamide (the pyridine v...
Silver complexes of a cation binding supramolecular host, resorcinarene bis-crown (CNBC5) with propyl, nonyl, decyl and undecyl alkyl chains were investigated by NMR titration, picrate extraction and single crystal X-ray diffraction. Binding studies showed that both 1 : 1 and 1 : 2 (host-Ag(+)) complexes are present in solution with only a slight e...
A group of seven resorcinarene bis-crown ethers (CNBC5) with two polyether bridges at the upper rim
and either propyl, butyl, pentyl, heptyl, nonyl, decyl or undecyl groups at the lower rim were
synthesized and their binding properties with Cs+ were investigated by NMR titration. The bis-crowns
form 1 : 2 complexes with Cs+ with binding constants o...
o-Nitroaniline functionalized resorcinarene octapodands 1-5 with pendant methyl, ethyl, pentyl, nonyl or 1-decenyl groups, respectively, were synthesized and their structural properties investigated using X-ray crystallography and NMR spectroscopy. The upper rim of each podand is identical containing flexible side arms, in which rotation around the...
The calixarenes and resorcinarenes are macrocyclic phenolic molecules that can be modified “à façon” and a wide range of chemical modification strategies have been published over the last 30 years. Because of their remarkable structural properties and their relative ease of chemical modification, they represent excellent and highly versatile bases...
The interaction of aminomethylated resorcinarenes with a red xanthene dye, rhodamine B, was investigated in chloroform, methanol and chloroform–methanol solutions using UV-vis, NMR and fluorescence spectroscopy. Aminomethylated resorcinarenes 1 and 2 shift the rhodamine B equilibrium from the zwitterion to the lactone form unlike reference compound...
The chicken genome contains a BBP-A gene showing similar characteristics to avidin family genes. In a previous study we reported that the BBP-A gene may encode a biotin-binding protein due to the high sequence similarity with chicken avidin, especially at regions encoding residues known to be located at the ligand-binding site of avidin.
Here, we e...
Dual chain avidin (dcAvd) is an engineered avidin form, in which two circularly permuted chicken avidin monomers are fused into one polypeptide chain. DcAvd can theoretically form two different pseudotetrameric quaternary assemblies because of symmetry at the monomer-monomer interfaces. Here, our aim was to control the assembly of the quaternary st...