Band 4, Heft 5 -

The present chapter will illustrate few examples of multi-technique and multi-scale approaches for objects belonging to past or modern periods in the history of art chronology. Thus, four studies on four different topics are brought to the attention: multi disciplinary and multi-techniques characterization of gilded altarpieces and sculptures in Portugal between 1500 and 1800 (3 years research project); an interdisciplinary approach to easel paintings from fifteenth and sixteenth century in Portugal (3 years research project); characterization of ketone resins varnishes (2 years research project) and of salts developed on canvas paintings from the Munch Museum collection (past investigation to be continued with an ongong 3 years research project). These studies show how important is to make use of different analytical tools when investigating a specific material, artistic technique or degradation phenomenon. The objects studied in the above mentioned research projects were created on wooden or canvas supports and they present paint, polichromy or gilded layers, and varnish coatings, therefore their structure and composition is complex and requires a complex, interdisciplinary approach. In many cases to the surface materials from a polychrome or painted object, degradation products are present and their identification as well the understanding of their mechanism of formation is possible only we have a complete overview of the materials present in the layered structure of the object.

Identification of proteinaceous materials in artworks is of high interest to restorers-conservators, art historians and archaeologists, because it helps to shed light on the used painting techniques, to attribute unknown artworks, to make conclusions on prehistoric diets, etc. The chapter is devoted to the mass spectrometry instrumentation, evaluation of obtained data and it is showing several examples of the application of matrix-assisted laser desorption/ionization–time-of-flight and liquid chromatography–electrospray ionization–quadrupole–time-of-flight mass spectrometers on cultural heritage samples.

Organic selenium- and tellurium-phosphorus compounds have found wide application as reagents in synthetic inorganic and organic chemistry, such as oxygen/chalcogen exchange, oxidation/reduction, nucleophilic/electrophilic substitution, nucleophilic addition, free radical addition, Diels–Alder reaction, cycloadditions, coordination, and so on. This chapter covers the main classes of phosphorus-selenium/tellurium reagents, including binary phosphorus-selenium/tellurium species, organophosphorus(III)-selenium/tellurium compounds, phosphorus(V)-selenides/tellurides, diselenophosphinates/ditellurophopshinates, diselenaphosphetane diselenides, Woollins’ reagent, phosphorus-selenium/tellurium amides, and imides. Given the huge amount of literature up to mid-2017, this overview is inevitably selective and will focus particularly on their synthesis, reactivity, and applications in synthetic and coordination chemistry.

The reactivity of the chalcogen–nitrogen bond toward main-group element or transition-metal halides, as well as electrophilic and nucleophilic reagents, is the source of a variety of applications of Se–N and Te–N compounds in both inorganic or organic chemistry. The thermal lability of Se–N compounds also engenders useful transformations including the formation of radicals via homolytic Se–N bond cleavage. These aspects of Se–N and Te–N chemistry will be illustrated with examples from the reactions of the binary selenium nitride Se 4 N 4 , selenium–nitrogen halides [N(SeCl n ) 2 ] + ( n = 1, 2), the synthons E(NSO) 2 (E = Se, Te), chalcogen–nitrogen–silicon reagents, chalcogen(IV) diimides RN=E=NR, the triimidotellurite dianion [Te(N t Bu) 3 ] 2− , chalcogen(II) amides and diamides E(NR 2 ) 2 (E = Se, Te; R = alkyl, SiMe 3 ), and heterocyclic systems.

Metal chalcogenides are technologically important materials. Physical, chemical, electrical and mechanical properties of these materials can be fine-tuned by manipulating their shape, size and composition. Although several methods are employed for their synthesis, single-source molecular precursor route has emerged as a versatile strategy for their synthesis and in controlling shape, size and composition of the material under moderate conditions. This chapter gives a brief coverage on the design and development of single-source molecular precursors which have been employed for the preparation of metal selenide/telluride nanocrystals and for deposition of thin films. The discussion includes synthesis of transition-, main group and f-block metal chalcogenolate and/or chalcogenide clusters as precursors and their conversion into metal chalcogenides in the form of thin films and nanostructures. Precursors for ternary metal chalcogenides are also included.

This chapter emphasizes aspects related to the role of organochalcogen (Se, Te) compounds with single E‒O and/or double E=O (E=Se, Te) bonds in organic synthesis, as reagents, intermediates, or catalysts, and it gives a larger extent mainly to data reported in the field during the last ten years. For each of these two heavier chalcogens the material is structured according to the oxidation state of the chalcogen and, for the same oxidation state, in sections dedicated to a particular type of compounds. Functionalization or cyclization reactions in which the organochalcogen compounds take part as nucleophiles, electrophiles or radicals, employed in various synthetic transformations, are discussed and, where available, the mechanistic aspects are outlined. New chiral species and new strategies were developed during last years in order to increase the yield, the reaction rate and the stereoselectivity in specific organic transformations, i.e. addition, oxidation, elimination, cyclization or rearrangement reactions. A notably attention was devoted to easily accessible and environmental friendly catalysts, re-usable and “green” solvents, as well as waste-free procedures.

This review summarizes results in the field of hydrogen-bond templated enantioselective photochemistry. It covers both the stoichemiometric use of templates derived from Kemp’s triacid as well as photocatalytic methods to achieve high enantioselectivities in photochemical processes.

Liquid chromatography has been widely employed in the analysis of materials in Heritage Science, due to its ease of use and relatively low-cost, starting from thin layer chromatography of organic binders in paintings, of archaeological waxes and resins, and finally of natural dyes. High performance systems employing analytical columns containing packed stationary phases gradually supplanted thin layer chromatography (TLC) in the field, since the separation, detection and quantitation of specific species contained in a sample in the field of Cultural Heritage requires selective, sensitive and reliable methods, allowing for analysing a wide range of samples, in terms of analyte types and concentration range. Today, the main applications of High-Performance Liquid Chromatography in this field are related to the separation and detection of dyestuffs in archaeological materials and paint samples by reversed-phase liquid chromatography with suitable detectors. Proteomics and lipidomics are also gaining momentum in the last decade, thanks to the increased availability of instrumentation and procedures. In this chapter, principles and theory of liquid chromatography will be presented. A short review of the instrumentation needed to perform an analysis will be provided and some general principles of sample preparation revised. More details on the detection systems, the chromatographic set-ups and specific sample treatment strategies will be provided in the individual sections dedicated to the applications to Heritage Science of the main types of liquid chromatographic techniques. In particular, the applications of thin layer chromatography will be shortly described in paragraph 4.1. The applications of Reverse Phase High Performance Liquid Chromatography (RP-HPLC) will be discussed in detail in paragraph 4.2, including the analysis of natural and synthetic dyes and pigments and the profiling of lipid materials. The possibility to perform proteomic analysis will be presented and a link to the relevant Chapter in this book provided. The most important and promising applications of ion exchange chromatography (IC) will be discussed in paragraph 4.3. Finally, size exclusion and gel permeation chromatography (GPC) will be presented in paragraph 4.4, including applications to the study of polymeric network formation in paint binders, of the phenomena related to the depolymerisation of cellulose in paper and of cellulose and lignin in wood samples. The possibility to study synthetic polymers as artists’ materials and restorers’ tools by size exclusion (SEC) or gel permeation (GPC) will also be introduced. In the conclusions, future perspectives of liquid chromatography in Heritage Science will be briefly discussed.

The chemical space of naturally occurring compounds is vast and diverse. Other than biologics, naturally occurring small molecules include a large variety of compounds covering natural products from different sources such as plant, marine, and fungi, to name a few, and several food chemicals. The systematic exploration of the chemical space of naturally occurring compounds have significant implications in many areas of research including but not limited to drug discovery, nutrition, bio- and chemical diversity analysis. The exploration of the coverage and diversity of the chemical space of compound databases can be carried out in different ways. The approach will largely depend on the criteria to define the chemical space that is commonly selected based on the goals of the study. This chapter discusses major compound databases of natural products and cheminformatics strategies that have been used to characterize the chemical space of natural products. Recent exemplary studies of the chemical space of natural products from different sources and their relationships with other compounds are also discussed. We also present novel chemical descriptors and data mining approaches that are emerging to characterize the chemical space of naturally occurring compounds.