Preface from the Guest Editor of Special Issue "Quantum-Chemical Modeling and Design of Chelate and Macrocyclic Metal Complexes".

As is known, in the last fifty years of coordination of inorganic and organo-elemental chemistry, chemical compounds formed by chelating or macrocyclic organic and organo-elemental ligands (in particular, crown ethers, cryptands, calixarenes, cucurbituryls, porphyrins, and their various derivatives) and ions of various p-, d- and f-elements, have become of special interest [...].