Provided herein are magnetic resonance imaging (MRI) contrast agents comprising a compound having a structure represented by: Y - X - Z, wherein, X is: Fe(III) or Mn(II), and Y and Z are each independently selected from pyrophosphate and bisphosphonate (e.g., 1-hydroxybisphosphonate), or a pharmaceutically acceptable hydrate and/or salt thereof. Methods of use of the MRI contrast agent are also provided.