Diaquabis(ethylenediamine)copper(II) vs. monoaquabis(ethylenediamine)copper(II): Synthesis, characterization, single crystal X-ray structure determination, theoretical calculations and antimicrobial activities of [Cu(en)2(H2O)2](2-phenoxybenzoate)2·H2O and [Cu(en)2(H2O)](diphenylacetate)2·3H2O