The reactions of cobalt(II) halides and flexible ligand L [L = 1,3-bis(pyrid-4-ylthio)propan-2-one] under different conditions generated a series of complexes with various structural motifs ranging from tetragonal-prismatic cages to 1-3D coordination polymers. The layer diffusion of cobalt(II) chloride and L in methanol/acetone at 25 degrees C gave rise to a 3D polymer, [Co(L)(2)Cl-2]center dot Me2CO (1). At 30 degrees C, the slow diffusion of diethyl ether into the blue dimethylformamide (DMF) solution of complex 1 afforded a 1D polymer, Co(L)Cl-2(DMF)(2) (2). However, at 10 degrees C, the diffusion of diethyl ether into the DMF solution of complex 1 produced a tetragonal-prismatic cage, [Co-2(L)(4)Cl-2]Cl(2)center dot Et2O center dot DMF center dot 2MeOH center dot 4H(2)O (3). The reaction of cobalt(II) bromide and L in DMF at 10 degrees C yielded a dimer, [Co-2(L)(4)Br-2]Br(2)center dot 6DMF center dot 2H(2)O (4), with a cage structure similar to 3. The preparation of the series of compounds indicates the subtle relationship between structures and tunable reaction conditions. It is also found that the structural motifs vary according to the ligand conformations and that the formation of tetragonal-prismatic cages 3 and 4 may be templated by anionic guests. Magnetic studies on complexes 1-4 in a temperature range 4-300 K disclose that L is unfavorable for a long-range magnetic interaction; however, intramolecular spin-coupling constants of -19.6 and -21.5 cm(-1) for 3 and 4 indicate rather strong magnetic superexchanges arising from the overlap of the d(z)(2) orbitals of the cobalt(II) and p, orbitals of the encapsulated halide anions. Electron paramagnetic resonance (EPR) spectra of complexes 3 and 4 in solution and solid give information that both complexes are high-spin cobalt(II) compounds with a rhombic distortion of the axial zero-field splitting. Interestingly, the intramolecular magnetic-exchange coupling in 3 and 4 mediated by the encapsulated anion Cl- or Br- is also reflected by the EPR spectra.