We describe herein the synthesis of generation 4 (G4) poly(amidoamine) (PAMAM) dendrimers bearing (1) a nitroaniline derivative as an NMR probe, (2) (eta(5)-cyclopentadienyl)iron dicarbonyl succinimidato complexes as infrared probes for carbonyl metallo immunoassay, (3) acetamide groups for increased solubility, and (4) hydrazide functions at the extremity of five-carbon atom spacer arms for the labeling of aldehyde-containing molecules. The step-by-step building of these multifunctionalized dendrimers was monitored by H-1 NMR spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Substitution of terminal amine groups of PAMAM dendrimers with appropriate functional groups provides complex dendrimeric structures with a wide range of applications. The final goal of this study is the development of new reagents suitable for the metal-carbonyl multilabeling of immunological reagents such as antibodies.