#$%^&*AU2016101702A420161020.pdf#####ABSTRACT The present invention provides a method of preparing a crystalline contrast agent for magnetic resonance imaging from a zwitterionic carboxylic pyridyl ligand and the crystalline contrast agent obtained or obtainable with said method. The crystalline contrast agent in 5 particular essentially consists of a manganese-organic or gadolinium-organic 3D framework. The present invention further provides a kit and a pharmaceutically acceptable composition comprising said crystalline contrast agent. The method of the present invention allows for preparing crystalline contrast agents with superior properties with easily available starting materials and with an economic and efficient process. The method allows for preparing 0 crystalline contrast agents with exceptional water-stability and water-solubility, which exhibit high longitudinal relaxivities and with excellent stabilities under physiological conditions and low cytotoxicity. Further provided is a method for in vivo imaging of a subject, in particular a human, comprising administering said crystalline contrast agent to the subject. 27
