Dioxatriazamacrocycle-N,N′,N′′-triacetic Acids (I): Synthesis, Protonation Constants, and Metal-Complex Studies. Crystal Structure of Hydrogen [1,4-Dioxa-7,10,13-triazacyclopentadecane-7,10,13-triacetato (4)-ϰN7,ϰN11,ϰN 13,ϰO7]copper(