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Model complexes of [FeFe]-hydrogenase bearing carboxylic acid functionalities have been designed for applications toward immobilization of hydrogen production electrocatalysts on amino-functionalized carbon electrode surfaces. Using carboxylic acid-substituted thiols, complexes incorporating the −COOH moiety into the thiolate linkers have been synthesized:  (μ-SCH₂CH₂COOH)₂[Fe(CO)₃]₂ (1) and the previously known (μ-(SCH₂)₂CHCOOH)[Fe(CO)₃]₂ (2). Carboxylic acid units have also been introduced via ligand substitution with a tricarboxyethyl phosphine to generate (μ-pdt)[Fe(CO)₃][Fe(CO)₂{P(C₂H₄COOH)₃}] (3). To mimic the linkage of complexes of these types to amino-functionalized monolayers, it has been demonstrated that 2 can be coupled with aniline in solution to generate (μ-(SCH₂)₂CHCONHPh)[Fe(CO)₃]₂ (4), and the stability of this linkage has been addressed. The carboxylic acid …