Abstract: A family of organometallic liquid absorbents that can have their thermophysical properties tailored for specific applications. Processes to manufacture these liquid absorbents and methods to optimize their thermodynamic properties are included. These organometallic liquid absorbents are used in compressor driven and heat driven heat pumps (50) and cryocoolers (99). With optimum thermodynamic properties, these heat pumps systems are highly efficient. These liquid absorbents are not damaging to the environment, are non-toxic and non-corrosive and are applicable to environmentally clean and highly efficient heat pumps, refrigerators, air conditioners, process heating and cooling systems, electronics cooling systems, cryocoolers and gas separation processes.