engleski

Aromatic dinitroso derivatives: interactions through azodioxide bonds in solution, solid state and on gold surface

Aromatic C-nitroso compounds and their Z- and/or E-azodioxy dimers exist in equilibrium in solution, which is usually shifted towards the monomers at ambient conditions.[1] Dimers can be formed by lowering the solution temperature or by crystallization. Compounds with two or more nitroso groups are able to form oligomers and polymers by interactions through multiple azodioxide bonds. Recently, we prepared several new aromatic dinitroso derivatives differing in spacer between two phenyl rings. Inspection of IR spectra revealed that in solid state these compounds are mostly present as E- or Z-oligomers. In order to investigate their possible dimerization or oligomerization in solution, we recorded one- and two-dimensional 1H NMR spectra at ambient and low temperatures. Analysis of NMR spectra indicated that aromatic dinitroso derivatives dimerize at low temperatures affording a mixture of nitroso monomers and Z- and/or E- azodioxides. The proton chemical shifts of nitroso monomer-azodioxide mixtures were assigned and validated by DFT calculations. In almost all cases, a preference towards the formation of Z- azodioxy isomer was found. In addition, we recently investigated self-assembly and possible dimerization of sulfur-containing aromatic dinitroso derivatives on gold surface by using polarization modulation infrared reflection- absorption spectroscopy (PM-IRRAS), atomic force microscopy (AFM), scanning tunneling microscopy (STM), ellipsometry and water contact angle goniometry.[2] The results obtained suggested that aromatic dinitroso compounds are able to dimerize on gold surface through E-azodioxide bonds. In comparison to their mononitroso counterparts, adsorption of aromatic dinitroso derivatives on gold surface results in the formation of less ordered layers.

Aromatic dinitroso compounds ; Azodioxide bonds ; Dimerization

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