Design of Novel Uncharged Organic Superbases: Merging Basicity and Functionality

Emerging organosuperbase families
Examples of emerging organosuperbase families

In a recent account Design of Novel Uncharged Organic Superbases: Merging Basicity and Functionality. Acc. Chem. Res. 2021, 54, 3108-3123 four groups doing research at the forefront of superbase chemistry – IOCB (Czech Republic), Rudjer Boskovic Institute (Croatia), Philipps-Universität Marburg (Germany) and our group at University of Tartu – have joined forces in charting the direction for further developments of the whole organosuperbases area. What synthetic chemists need, are “non-ionic, metal-free superbases as chemically stable neutral organic compounds of moderate molecular weight, with intrinsically high thermodynamic basicity, adaptable kinetic basicity, and weak or tunable nucleophilicity at their basicity centres”. Such superbases would be are useful, being able to catalyze a number of reactions that are impossible otherwise.

The account demonstrates that just trying to achieve ever higher basicity is not the main challenge. Very high basicities have been demonstrated, both computationally and experimentally. Instead, the combination of high basicity with moderate molecular weight, ease of synthesis and stability is the key issue.

The account starts with the state of the art of neutral organic superbase research, theirs synthesis and basicity measurements, as well as computations and thereafter presents several examples of emerging organosuperbase families (see the Figure on the left) and discusses their synthesis, basicity and demonstrated, as well as potential applications.

Dr. Merit Oss, PhD thesis on the ionization efficiency in ESI

On the 24th of August, 2021, Merit Oss successfully defended her PhD thesis titled “Ionization efficiency in electrospray ionization source and its relations to compounds’ physico-chemical properties” 

The thesis by Merit revolves around ionization efficiency in electrospray ionization (ESI) MS. The main aim was to gain a better understanding of the relations between different molecular properties of compounds and the signal intensities of their ions in ESI-MS. During this study, a large number of ionization efficiency values were obtained. Eleven molecular parameters were taken into account for estimating their importance for evaluating the compound’s ionization efficiency in ESI. It was concluded that in the studied solvent system, a compound’s ionization in the ESI source is determined by its basicity, molecular size, and hydrophobicity/lipophilicity. The results showed that the obtained models for estimating compounds’ ionization efficiency can be used for approximate prediction. 

Congratulations, Merit! We wish you all the best for your future. 

 

Dr. Eliise Tammekivi – PhD thesis on the quantitative analysis of oils

Last Friday, on August 27, 2021, Eliise Tammekivi successfully defended her PhD thesis titled Derivatization and quantitative gas-chromatographic analysis of oils.

In the PhD thesis by Eliise, four derivatization procedures that are widely used for the analysis of oils in cultural heritage or archaeology were compared based on quantitative gas-chromatographic (GC) analysis. It was seen that the TMTFTH derivatization was the most suitable one for the GC analysis of fresh oils. An in-depth uncertainty estimation was performed for one of the derivatization procedures using the ISO GUM approach and the Monte Carlo method. Another one of the improved procedures was applied for the analysis of self-made artificially aged paint samples that had varying pigment to linseed oil ratio to see if the pigment concentration had an effect on the drying of the paint samples.

Additionally, small samples from two paint case study samples relevant to the history of Estonia – crucifix from Karja church and cupboard from Ruhnu island – were analyzed to obtain information about the materials in the paint samples. Finally, the improved quantitative method was used to quantify fatty acids present in yeast cells. 

Congratulations to you, Eliise!  

 

New publication: Classification of archaeological adhesives

Our group recently published a new article: Classification of archaeological adhesives from Eastern Europe and Urals by ATR-FT-IR spectroscopy and chemometric analysis. Archaeometry, 2021, 1–18

In this study, 100 adhesive samples, collected from hafting tools and ceramic containers as well as some adhesive lumps were analyzed using ATR-FT-IR in combination with PCA-based DA classification. The aim of this study was to discover the capabilities of ATR-FT-IR-DA classification as a potential screening method for the identification and grouping of different archaeological adhesive samples, and subsequently reduce the use of laborious GC-MS analysis.

100 archaeological adhesives were classified into 3 groups: bitch bark tar without major additives (72), birch bark tar with additives (13) and minor/non birch bark tar samples (15). Birch bark tar containing adhesives were separated from minor/non birch bark tar samples. Samples identified as birch bark tar without major additives were further classified possibly by their location, age or cultural specific manufacturing practices. The classification results were confirmed by GC-MS analysis of 9 archaeological samples selected from three compositional groups.

The study proves that ATR-FT-IR-DA classification is a non-destructive, rapid and reliable pre-scanning method for analyzing archaeological adhesives, especially suitable for small samples. Based on the results of ATR-FT-IR spectroscopic analysis, DA classification can help further distinguish samples with different backgrounds such as sample age, initial production, environmental conditions and site-specific preservation. GC-MS analysis could be used as a supplementary/confirmatory method to investigate samples with complex components and provide archaeological DA references for future research.

The full text can be found here.

Dr. Astrid Darnell – PhD thesis on the study of anion receptors

On the 20th of May, 2021, Astrid Darnell defended her PhD thesis titled “Computational design of anion receptors and evaluation of host-guest binding“. 

In the thesis by Astrid, the main aim was to study possible new receptor molecule candidates with computational methods. This could improve the design of receptors used for the detection of various important anions (including glyphosate dianion and small monocarboxylate anions). 

The suitability of the COSMO-RS method was tested for studying receptor molecule and anion binding. It was also demonstrated that COSMO-RS was shown to predict correctly the most stable conformers of the majority of the studied molecules. 

The effects of receptor and complex geometries and the spatial matching between host and guest species on the binding affinity of large, structurally complex receptors was investigated towards a selection of analytically interesting carboxylate anions. A number of these receptor structures are now being investigated for practical applications as real carboxylate anion sensors in the form of SC-ISEs.

The final part of the study investigated the applicability of isothermal titration calorimetry (ITC) experiments for the determination of the thermodynamic parameters (e.g. reaction entalphy ΔH) of host-guest binding reactions. Low-volume ITC experiments were found to be applicable for the study of low-affinity host-guest binding reactions and the combined standard uncertainty for reaction entalphy determination for these experiments is in the range of 1-2kJ/mol.

Congratulations to you, Astrid!

Measurement uncertainty online course 8th run has successfully finished!

On May 13, 2021, the online course (MOOC) Estimation of measurement uncertainty in chemical analysis offered by the University of Tartu finished successfully.

Eventually, altogether 950 people registered from 97 countries. 501 participants actually started the course (i.e. tried at least one graded test at least once). The overall completion rate was 33%. This, as well as the participating rate, was the lowest (53%) we have seen. However, the completion rate of the participants who started the studies was 63% with 314 successfully finished participants. This result can be considered very good for a MOOC, especially for one that has quite difficult calculation exercises, which need to be done correctly for completing the course. All statistics during the 8 years can be found in the table below.

The participants were very active and asked lots of questions. The questions were often very much to the point and addressed things that are really important to analysts in their everyday work. The course has several forums (general and by topic) and during the course period the overall number of forum posts was close to 400 (!) (overall number of posts, both from participants and from teachers) and the forums are still active and posts are still coming in.

We want to thank all participants for helping to make this course a success!

We plan to repeat this course again in Spring 2022.

Dr. Matti Laan – Laser cleaning in cultural heritage

Yesterday, on the 7th of May, Associate Professor emeritus of physics Matti Laan gave a highly interdisciplinary lecture about laser cleaning in the field of cultural heritage.

On this project, Dr. Laan (presenting his lecture in the picture on the right) worked with the late Associate Professor emeritus of chemistry Tullio Ilomets. Dr. Laan gave an exciting lecture about different lasers (e.g., Nd:YAG, XeCl, Er:YAG) and which of them is most suitable for laser cleaning of various artefacts (such as paintings or sculptures). For this laser ablation is used, which removes any undesired material (including ageing products and materials from previous conservation works) layer by layer.

Most of the listeners participated via the Zoom platform – over 70 physics, chemists, conservators, material scientists, and people from other disciplines joined in this interdisciplinarity lecture. The lecture was organised by our Cultural Heritage workgroup, Institute of Physics, and The Estonian Academy of Arts in the framework of Dr. Signe Vahur’s PRG1198. The recording (in Estonian) can be found here.

Webinar “Mobile Phase pH in Liquid Chromatography”

On Apr 29, 2021 the webinar “Mobile Phase pH in Liquid Chromatography” was organised in the framework of the project 17FUN09 “UnipHied” (www.uniphied.eu). Altogether 101 people participated from 41 countries, ranging from Portugal to Philippines and from Peru to Nepal.

It is well known that in liquid chromatography, mobile phase pH is an important parameter, significantly affecting the retention of acidic and basic analytes. Yet, mobile phase pH is tricky to measure because mobile phases are usually aqueous-organic mixtures and in the case of gradient elution mobile phase composition gradually changes during elution. The topics covered during the webinar were:

— Different possibilities to express pH in liquid chromatography (LC)
Unified pH (pHabs): the concept and measurements methods
— The applications and limitations of different pH expressions in LC

Numerous questions were asked by the participants that indicated the importance of the topic and the need for a more robust conceptual framework for handling the topic of pH in liquid chromatography. Contributing to this, via the pHabs concept, is one of the aims of the UnipHied project.

The UnipHied project is funded from the EU’s EMPIR programme, co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. Additional support from: EU Regional Development Fund (TK141 “Advanced materials and high-technology devices for energy recuperation systems”), Estonian Research council (PRG690) and Estonian Center of Analytical Chemistry (www.akki.ee)


 

 
 
 

New Open Access publication: GC-MS analysis of aged oil paints

Our group recently published a new Open Access research article – Quantitative GC-MS Analysis of Artificially Aged Paints with Variable Pigment and Linseed Oil Ratios, Molecules 2021, 26 (8), 2218

In this freely accessible publication, seven sets of artificially aged paints prepared from a pigment (chrome oxide green, natural cinnabar, Prussian blue, red ochre, hematite + kaolinite, zinc white, or yellow ochre) and linseed oil were analysed with GC-MS. One of the main aims was to study if the pigment concentration in the paint samples affects the drying of the linseed oil. 

The palmitic acid to stearic acid ratio (P/S), azelaic acid to palmitic acid (A/P), and the relative content of dicarboxylic acids (∑D) showed, that besides the type of the pigment, also the concentration of the pigment can influence these values that are commonly used to identify the type of the oil or to characterize how dried is the sample. 

The absolute quantification of stearic acid (see figure on the right) showed that the drying of all paint sets (except for zinc white) were influenced by the pigment concentration. Therefore, this is another factor that needs to be taken into account when studying aged oil paints. 

 

 

Dr. Signe Vahur has been presented to the AcademiaNet!

This year the Estonian Research Council has presented 49 female Estonian scientists to the AcademiaNet database. From the Unversity of Tartu, seven names were given, including Dr Signe Vahur (on the picture), a research fellow in our Chair of Analytical Chemistry.

The AcademiaNet contains profiles of excellent female researchers from all disciplines. The database enables wider recognition worldwide, allowing scientists and research institutions to search for suitable collaborations, experts, or speakers. The database was initiated in 2010 and, by now, has the profiles of 3000 outstanding female researchers from all over the world.

Since 2003, Dr Signe Vahur has done research in the field of conservation science and specialized in the investigation of cultural heritage objects (paints, textiles, paper, resinous materials, etc.) with a vast collection of instrumental techniques. She has also worked as a conservator of polychrome objects and now is the leader of our Cultural Heritage workgroup. Recently, her team started to develop a new device that could be used to analyze valuable cultural heritage objects, so there’s only more to come!

Signe, congratulations from us all!