Anchor Groups Effect on Spectroscopic and Electrochemical Properties of Quaternary Nanocrystals Cu–In–Zn–S Capped with Arylamine Derivatives

A two-step procedure is reported enabling preparation of quaternary Cu–In–Zn–S nanocrystals with electrochemically active ligands consisting of 4-dodecylphenylaminobenzene and amine, thiol, or carboxylic anchor groups. Detailed ¹H NMR and IR studies of nanocrystals dispersion as well as free ligands recovered via nanocrystals dissolution indicate that in the organic shell of initial ligands weakly (1-octadecene (ODE)) and more strongly (1-dodecanethiol (DDT) and oleylamine (OLA)) bound ligands coexist. Treating the nanocrystals with pyridine removes weakly bound ligands; however, DDT and OLA molecules remain present as coligands with pyridine. Labile pyridine ligands can then be exchanged for the target 4-dodecylphenylaminobenzene derivatives with different anchor groups. ¹H NMR lines of these ligands are broadened due to their restricted rotation; this broadening is especially pronounced for the lines corresponding to the anchor group protons. Electrochemical activity of the ligands is significantly altered after their binding to the nanocrystal surface. Strongly interacting anchor groups such as −Ph–SH or −Ph–CH₂NH₂ lose their electrochemical activity upon coordination to nanocrystals, and weakly interacting groups (−PhNH₂) retain it. Secondary amine −Ph–NH–Ph– remains electrochemically active in all nanocrystals capped with the studied ligands; however, the potential of its oxidation depends on the conjugation with the anchor group

Self-Assembly Properties of Semiconducting Donor–Acceptor–Donor Bithienyl Derivatives of Tetrazine and ThiadiazoleEffect of the Electron Accepting Central Ring

Scanning tunneling microscopy was used to study the effect of the electron-accepting unit and the alkyl substituent’s position on the type and extent of 2D supramolecular organization of penta-ring donor–acceptor–donor (DAD) semiconductors, consisting of either tetrazine or thiadiazole central acceptor ring symmetrically attached to two bithienyl groups. Microscopic observations of monomolecular layers on HOPG of four alkyl derivatives of the studied adsorbates indicate significant differences in their 2D organizations. Ordered monolayers of thiadiazole derivatives are relatively loose and, independent of the position of alkyl substituents, characterized by large intermolecular separation of acceptor units in the adjacent molecules located in the face-to-face configuration. The 2D supramolecular architecture in both derivatives of thiadiazole is very sensitive to the alkyl substituent’s position. Significantly different behavior is observed for derivatives of tetrazine (which is a stronger electron acceptor). Stronger intermolecular DA interactions in these adsorbates generate an intermolecular shift in the monolayer, which is a dominant factor determining the 2D structural organization. As a consequence of this molecular arrangement, tetrazine groups (A segments) face thiophene rings (D segments) of the neighboring molecules. Monolayers of tetrazine derivatives are therefore much more densely packed and characterized by similar π-stacking of molecules independently of the position of alkyl substituents. Moreover, a comparative study of 3D supramolecular organization, deduced from the X-ray diffraction patterns, is also presented clearly confirming the polymorphism of the studied adsorbates

Structural, Spectroscopic, Electrochemical, and Electroluminescent Properties of Tetraalkoxydinaphthophenazines: New Solution-Processable Nonlinear Azaacenes

A series of solution-processable tetraalkoxy-substituted dinaphtho­[2,3-<i>a</i>:2′,3′-<i>h</i>]­phenazines were synthesized by reductive functionalization of indanthrone (6,15-dihydrodinaphtho­[2,3-<i>a</i>:2′,3′-<i>h</i>]­phenazine-5,9,14,18-tetraone), an old intractable dye. The melting point of these new compounds was found to decrease from 204 °C to 98 °C upon extension of the number of carbons from 4 to 12 in the alkoxy substituent. All derivatives show a strong tendency to self-organize in 2D as evidenced by STM investigations of monolayers deposited on HOPG. The 2D structure is less dense and shows different alkoxy group interdigitation pattern as compared to the 3D structure determined from the X-ray diffraction data obtained for the corresponding single crystals. Electrochemical, absorption, and emission properties of tetraalkoxy-substituted dinaphtho­[2,3-<i>a</i>:2′,3′-<i>h</i>]­phenazines, studied in solution, are essentially independent of the length of the alkoxy substituents. All derivatives exhibit high photoluminescence quantum yield, approaching 60%. When molecularly dispersed in a solid matrix consisting of poly­(9-vinylcarbazole) (PVK) (60 wt %) and (2-<i>tert</i>-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) (40 wt %) (so-called “guest/host configuration”), they show green electroluminescence due to an effective energy transfer from the matrix to the luminophore. The best light-emitting diodes were obtained for the butoxy derivative showing a luminance approaching 1500 cd/m² and a luminous efficiency over 0.8 cd/A