Three-dimensional networks of hydrogen bonds in periodic arrays of molecular modules containing amide-(ethylene glycol) and amide-(ethylene glycol)-amide: Ab initio picture

First-principle modeling is used to identify the most likely conformations of two molecular modules A(EG)3,6 and A(EG)3,6CH2A (A = CONH, EG = (CH2)2O), which in self-assembled monolayers form, respectively, one- and two-layered networks of hydrogen-bonded amides (HBAs). The molecular bond lengths and angles within HBA chains, which are formed within ( 3 × 3 ) R 30 ∘ hexagonal arrays of identical modules, were calculated by exploiting the DFT/BP86/6-31G method. The results from our first-principle conformation analysis highlight an integrated picture of hydrogen bonding in related families of assemblies containing one and two amide groups per molecule, e.g., in HS–(CH2)nA(EG)mH and HS–(CH2)nA(EG)mCH2A–(CH2)lH SAMs on gold.