Three novel Mn-III polymers, Mn(phox)(2)(N-3)](n) (1), [Mn(Etphox)(2)(N-3)](n) (2), and [Mn(Etphox)(2)(C2N3)](n) (3), using achiral ligand Hphox (Hphox = 2-(4,5-dihydrooxazol-2-yl)phenol) and chiral ligand HEtphox (HEtphox = 2-(4-ethyl-4,5-dihydrooxazol-2-yl)phenol) were synthesized and structurally and magnetically characterized. All complexes are of 1D chain structures and form 2D frameworks by weak interactions. The adjacent 1D chains of complex 1 are connected by face-to-face.pi-pi interactions, C-H center dot center dot center dot pi interactions, and hydrogen bonding, which leads to the formation of a supramolecular 2D sheet structure. The three compounds show antiferromagnetic coupling between Mn-III ions. And compound 2 is a spin-canted weak ferromagnet with T-N=5.6 K, showing metamagnetic behavior with a two-step magnetic phase transition.