University of Zagreb. Faculty of Science. Department of Chemistry.
Abstract
We present a computational study of self-assembled monolayers (SAMs) of several functional
molecules which share a triptycene core and differ in the number of anchoring groups and
functional mounts (photoswitches or light-driven motors). Structural properties of different
SAMs on the water-air interface are explored by nanoscale molecular dynamics carried out in
the tight-binding DFT formalism, as well as by static meta-GGA DFT calculations. Both
approaches give similar results, revealing that tilting and bending in SAMs is significant in all
investigated systems. Molecular dynamics shows that SAMs tilt collectively, although the
motion of individual machines is not strongly correlated. Functional heads, triptycenes and
anchoring groups are found to strongly affect SAM properties, and a structure bearing two
triptycene units and three anchoring groups is identified as the most promising future synthetic
target. Finally, the computational results are validated by comparing them with previously
performed experiments (anisotropic spectroscopy and ellipsometry).U ovom radu računalnim su metodama istraženi samoudruženi monoslojevi (SAM) niza
funkcionalnih molekula koje se razlikuju po funkcionalnoj jedinici (sklopka ili svjetlom
upogonjeni motor) i broju veznih skupina, a dijele tripticensku jezgru. Strukturna svojstva
različitih SAM-ova na međupovršini voda-zrak istražena su nanosekundnom molekulskom
dinamikom provedenom u formalizmu DFT modela čvrste veze, te meta-GGA DFT statičkim
izračunima. Oba pristupa daju slične rezultate i otkrivaju da su, u svim proučavanim sustavima,
molekule značajno nagnute i savinute. Rezultati molekulske dinamike pokazuju da je nagibanje
SAM-ova kolektivan proces, iako gibanje individualnih strojeva nije korelirano. Također,
potvrđeno je da funkcionalne glave, tripticeni i vezne skupine značajno utječu na svojstva
monoslojeva, te je kao glavni kandidat za sintezu novih funkcionalnih materijala identificiran
molekulski sustav s dvije tripticenske jedinice i tri vezne skupine. Usporedbom s prethodno
provedenim eksperimentima (anizotropnom spektroskopijom i elipsometrijom) potvrđeni su
računalni rezultati