Spectroscopic and structural investigation on the pentachloro- and (mixed-pentahalo)cuprates(II) of the N-(2-ammoniumethyl)piperazinium cation. The first case of monomeric pentahalocuprate(II) having square-pyramidal structure. Crystal and molecular structure of the (N-(2-ammoniumethyl)piperazinium) pentachlorocuprate(II) dihydrate