A lanthanide 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 2: where: E represents a heteroatom or heteroatom-containing group and R1-R8 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.