The present invention relates to pyrazine derivatives such as those represented by Formulas I and II. X1 to X4 of Formulas I and II may be characterized as electron withdrawing groups, while Y1 to Y4 of Formulas I and II may be characterized as electron donating groups. Pyrazine derivatives of the present invention may be utilized in assessing organ (e.g., kidney) function. In a particular example, an effective amount of a pyrazine derivative that is capable of being renally cleared may be administered into a patient's body. The pyrazine derivative may capable of one or both absorbing and emanating spectral energy of at least about 400 nm (e.g., visible and/or infrared light). At least some of the derivative that is in the body may be exposed to spectral energy and, in turn, spectral energy may emanate from the derivative. This emanating spectral energy may be detected and utilized to determine renal function of the patient.