Compounds represented by the following general formula (I): R-Y-(-X-Phe-COCH2COCnF2n+1)m (I) wherein R represents hydrogen, alkyl, phenyl or a group capable of binding to a protein, a peptide, an amino acid, a nucleic acid or a base; Y represents CH2, a carbon ring or a heterocycle; X represents O, S, NH, CH2, OCH2, CONH or NHCO; Phe represents phenylene; n is an integer of from 1 to 5; and m is 1, 2 or 3; luminous complexes comprising the above compounds with rare earth ions; labeling reagents comprising the compounds or luminous complexes as described above; and a method of labeling a protein, a peptide, an amino acid, a nucleic acid or a base using the above labeling reagents.