Solvation of dicarboxylate dianions of varying length of the aliphatic chain in water clusters 
and in extended aqueous slabs was investigated using photoelectron spectroscopy and molecular 
dynamics simulations.  Photoelectron spectra of hydrated succinate, adipate, and 
tetradecandioic dianions with up to 20 water molecules were obtained.  Even-odd effects were 
observed as a result of the alternate solvation mode of the two negative charges with 
increasing solvent numbers.  The competition between hydrophilic interactions of the charged 
carboxylate groups and hydrophobic interactions of the aliphatic chain leads to conformation 
changes in large water clusters containing dicarboxylates bigger than adipate. It also leads 
to a transition from bulk aqueous solvation of small dicarboxylates to solvation at the 
water/vapor interface of the larger ones. While oxalate to adipate solvate in the inner 
parts of the aqueous slab, suberate and longer dicarboxylate dianions have a strong propensity 
to the surface. This transition has also consequences for the folding of the flexible 
aliphatic chain and for the structure of aqueous solvation shells around the dianions.