A Ianthanide complex, method of forming and method of using the lanthanide complex as a near-infrared luminescent material are described. The complex includes at least one lanthanide ion and at least one polydentate ligand derived from a molecule having the general formula of Structure: Structure 2, where: E represents a heteroatom or heteroatom-containing group and R1R8 are independently selected from H, —OH, —NH2, —SO3H, —CO2H, halides, optionally substituted organic groups and conjugated linking groups which link two of the polydentate ligands of Structure 2 together.
