The synthesis and characterisation of seven iron(II) 1D chain coordination polymers with tetradentate Schiff-base like equatorial ligands and bis(4-pyridylmethyl)sulfide (bpms) as a flexible bridging axial ligand is reported. This new family of materials displays a wide spectrum of spin transition properties in the solid state ranging from gradual, abrupt, incomplete to even step-wise that have all been characterized by SQUID magnetometry. The X-ray structure analysis of two complexes at several temperatures is discussed in the frame of their spin crossover properties.