Two Series of Novel Rare Earth Complexes with Dicyanamide [Ln(dca) 2 (phen) 2 (H 2 O) 3 ][dca]·(phen), (Ln = Pr, Gd, and Sm) and [Ln(dca) 3 (2,2‘-bipy) 2 (H 2 O)] n , (Ln = Gd, Sm, and La):  Syntheses, Crystal Structures, and Magnetic Properties