Phenothiazine Cruciforms:  Synthesis and Metallochromic Properties

Abstract

We report the synthesis and characterization of five novel phenothiazine-containing cruciforms (5-9). The targets were prepared by a NaH-promoted Horner reaction of tetraethyl(2,5-diiodo-1,4-phenylene)bis(methylene)diphosphonate with 10-hexyl-10H-phenothiazine-3-carbaldehyde. The formed intermediary 3,3'-(1E,1'E)-2,2'-(2,5-diiodo-1,4-phenylene)bis(ethene-2,1-diyl)bis(10-hexyl-10H-phenothiazine) was reacted with several different aromatic alkynes (1-tert-butyl-4-ethynylbenzene, N,N-dibutyl-4-ethynylaniline, 1-ethynyl-3-(trifluoromethyl)benzene, and 1-ethynyl-3,5-bis(trifluoromethyl)benzene) to give the corresponding cruciform fluororphores (XF). The XFs were fully characterized by NMR and IR spectroscopy and then exposed to trifluoroacetic acid as well as to several metal triflates. The XFs show dramatic shifts in emission and to a lesser extent in absorption when exposed to magnesium triflate or zinc triflate. In the case of magnesium triflate, a blue shift in emission was observed; in contrast, addition of zinc triflate results in either quenching or a red-shifted emission. Due to the electronic situation, these XFs display spatially separated frontier molecular orbitals, allowing the HOMO or the LUMO of the XFs to be addressed independently by addition of zinc or magnesium ions. Phenothiazine XFs may have potential in array-type sensory applications for metal cations.

Synthesis, Electronic, and Electro‐Optical Properties of Emissive Solvatochromic Phenothiazinyl Merocyanine Dyes

“…In addition, modular strategies have enabled straightforward accesses to structurally well-defined monodisperse electronically coupled oligophenothiazines with direct 3,7-ligation (Scheme 1) of the units. [14a, 24] Interestingly, the emission behavior of phenothiazine derivatives such as cyanoA C H T U N G T R E N N U N G (oligo)-phenothiazines, [14b] and diphenothiazine dumbbells bridged by carbo- [25] and heterocycles, [14c] and cruciforms [26] reveals enormous Stokes shifts and, thus, has aroused our interest for a deeper understanding of the excited-state structure and properties. Here, we report the syntheses and investigation of ground-and excited-state electronic properties of various phenothiazinyl merocyanines with tunable emission and redox properties.…”

Synthesis and Electronic Properties of Monodisperse Oligophenothiazines

“…[21] Therefore, in continuation of our program to synthesize and study bi-and terphenothiazines with alkynyl, [22] alkenyl, [23] aryl, [24] and organometallic [25] bridges and to explore their applications to PET systems, [26] we also became interested in higher oligomers of phenothiazine as low molecular weight representatives of polyphenothiazines. Here we report the synthesis of a homologous series of oligophenothiazines, together with correlation of their actual molecular weights and gel permeation chromatography, computed structures, and first electronic properties (cyclic voltammetry, absorption and emission spectroscopy).…”

Insights into Sonogashira Cross‐Coupling by High‐Throughput Kinetics and Descriptor Modeling

“…[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Sonogashira coupling is applied for producing pharmaceutical intermediates, liquid crystals, polymers, and materials with specialized optical and electronic properties. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Despite these numerous applications, our mechanistic understanding of the Sonogashira reaction is limited. [39,40] This is because the Sonogashira reaction, like other coupling reactions, has a complex catalytic cycle that involves several steps.…”