In the scope of its subject, chemistry occupies an intermediate position between physics and biology.[6] It is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level.[7] For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties of the soil on the moon (cosmochemistry), how medications work (pharmacology), and how to collect DNA evidence at a crime scene (forensics).
Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists.[14] Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; some of them are:[15]
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Chemistry was preceded by its protoscience, alchemy, which operated a non-scientific approach to understanding the constituents of matter and their interactions. Despite being unsuccessful in explaining the nature of matter and its transformations, alchemists set the stage for modern chemistry by performing experiments and recording the results. Robert Boyle, although skeptical of elements and convinced of alchemy, played a key part in elevating the "sacred art" as an independent, fundamental and philosophical discipline in his work The Sceptical Chymist (1661).[33]
At the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. In 1897, J.J. Thomson of the University of Cambridge discovered the electron and soon after the French scientist Becquerel as well as the couple Pierre and Marie Curie investigated the phenomenon of radioactivity. In a series of pioneering scattering experiments Ernest Rutherford at the University of Manchester discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles.
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Contrast-enhanced magnetic resonance imaging (MRI) has become an indispensable non-invasive diagnostic tool since the FDA approval of Gd-DTPA in 1988.1 However, lately, physicians have reported nephrogenic systemic fibrosis in patients with poor kidney function and a history of Gd-based contrast agent use for MRI scans.2 This has led to safety concerns that limit the use of Gd-based contrast agents and ultimately have sparked the search for alternative contrast agents. Mn2+ being an essential divalent metal ion makes an attractive alternative to Gd3+ as it offers ideal properties for efficient T1-weighted MR imaging probes such as 5/2 spin quantum number, rapid water-exchange rates, and long electronic relaxation time.3 In addition to that, the positron emitter manganese-52g is of increasing clinical relevance for its use for PET imaging3 as well as for manganese-52g/55 based bimodal PET/MRI agents. To harness the potential of Mn2+ ion for MRI and PET applications, we are working on developing a library of acyclic chelators using fundamental principles of coordination chemistry. Here, I will talk about the design and development of new heptadentate chelators with N5O2 donor set consisting of three pyridine rings and ethanolamine/carboxylate arms. The ligand, H2PyMEA has been characterized by 1H NMR and 13C NMR and its coordination chemistry has been investigated with 3d transition metal ions (Mn2+, Cu2+, Fe2+, and Zn2+) by employing UV-Vis absorbance spectroscopy, 1H NMR, and mass spectroscopy. Ligand synthesis, characterization and preliminary relaxometry studies of the Mn2+-H2PyMEA complex will be discussed along with ongoing synthesis of another ligand, H2PyGly.
Natural enzymes carry out organic transformations efficiently via pre-organizing substrates inside hydrophobic cavities to achieve selectivity and specificity during reaction turnover. Chemists have mimicked the enzymes by creating supramolecular cavities which can serve as active sites for catalysis. Recently it has been demonstrated that organic C-H activation reactions can be carried out inside a metal-based cationic water-soluble nanocage with visible light activation. To completely report a metal-free photoactivation scheme for carrying out catalysis, we planned to synthesize an all-organic cationic nanocage ExBox4+. By incarcerating a series of polyaromatic hydrocarbon (PAH) guests inside the ExBox4+ we were able to generate host-guest CT states that enabled a completely new metal-free C-H activation chemistry in acetonitrile under ambient conditions. The characterization of the host-guest complexes with PAHs of different sizes and their photoexcited dynamics for C-H bond activation using transient absorption spectroscopy will be discussed in the first part of the talk.
The thrust of my future research will be focused on understanding the fundamental mechanism(s) of VSC and to explore its potential applications in different fields of chemistry. For instance, so far only about a dozen chemical reactions have been studied under VSC and so much remains to be understood to explain how VSC induces such large changes in reactivity. In another direction, the perturbation of solute-solvent interactions under VSC clearly opens a new pathway in the field of chemical equilibria, supramolecular assembly, and crystal engineering that need to be further investigated.3-4 VSC undoubtedly will become a useful tool in chemistry and material science. It will also contribute to the fundamental understanding of the role of vacuum field in common molecular processes. 2ff7e9595c
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