Citigroup closed on the repurchase of its Tribeca headquarters at 388-390 Greenwich Street from SL Green Realty for $1.76 billion, according to public records filed with the city Monday. The banking giant sold the two buildings to SL Green and Ivanhoe Cambridge for $1.6 billion in 2007. At the time, it secured an option to repurchase the buildings, which it now made use of. The Real Deal reported Citigroup’s plans to buy back the tower in January.