Dihydroquinazoline FeII complexes, namely [Fe(pq-R)2](X)2·xCH3OH·yCH3CN·zH2O (R = 2-py: X = ClO4−, x = 1, y = 0, z = 2 (1), BF4−, x = 0, y = 2, z = 1.75 (2), CF3SO3−, x = 1, y = 1, z = 0 (3); and X = ClO4−: R = 2-OCH3, x = 0, y = 0, z = 1 (4), R = 3-OCH3, x = 0, y = 0, z = 1 (5)), were prepared and the effects of the solvent, counteranion and ligand substituent on spin crossover properties were discussed. Comparison of X-ray diffraction data for these complexes revealed the sole presence of high-spin FeII at 298 K and the bond distances around the FeII center at low temperature fall much closer to those at high temperature, which is consistent with variable-temperature dc magnetic susceptibility data. However, the loss of solvent induced a significant change in the spin state of complexes 1 and 2. Moreover, fits to magnetic data of the desolvated samples provide crossover temperatures of T1/2 = 182.9(6), 157.0(8) and 138.3(5) K for 1-des (ClO4−), 2-des (BF4−) and 3-des (CF3SO3−), respectively, indicative of the anion-dependent transition temperature. The cooperativity operating in the complexes is thought to be mainly from the intermolecular π⋯π interactions between dihydroquinazoline rings on the neighboring molecules. The ligand substituent effect was also investigated on FeII SCO properties. This work revealed the spin crossover properties of new types of dihydroquinazoline Fe(II) complexes, including the transition temperature, the degree of completion and the cooperative nature of the transition, which can be optimally designed when developing new spin-crossover materials.

•Chiral coordination polymers were obtained from achiral ligand.•Chirality resolution is related with the solvolysis of ligand.•Racemic and chiral products were separated in controllable manner.Through controlling the in-situ methoxyl addition that consequently switches the metal-chelation effect, a one-dimensional helical coordination polymer (1) and a chiral congeners (P-2 and M-2) were prepared, the 41 helice of opposite chirality in complex 1 are stacked alternately to form a racemate, while the 41 and 43 helices in the other are assembled homochirally by metal-chelation effect to generate a conglomerate, P-2 and M-2, respectively.Through controlling the in-situ methoxyl addition that consequently switches the metal-chelation effect, a racemic one-dimensional helical coordination polymer and a chirality-resolved congener were isolated.