Evaluation of the Intramolecular Charge-Transfer Properties in Solvatochromic and Electrochromic Zinc Octa(carbazolyl)phthalocyanines

Abstract

2,3,9,10,16,17,23·24-Octakis-(9H-carbazol-9-yl) phthalocyaninato zinc(II) (3) and 2,3,9,10,16,17,23·24-octakis-(3,6-di-tert-butyl-9H-carbazole) phthalocyaninato zinc(II) (4) complexes were prepared and characterized by NMR and UV-vis spectroscopies, magnetic circular dichroism (MCD), matrix-assisted laser desorption ionization mass spectrometry, and X-ray crystallography. UV-vis and MCD data are indicative of the interligand charge-transfer nature of the broad band observed in 450-500 nm range for 3 and 4. The redox properties of 3 and 4 were probed by electrochemical and spectro-electrochemical methods, which are suggestive of phthalocyanine-centered first oxidation and reduction processes. Photophysics of 3 and 4 were investigated by steady-state fluorescence and time-resolved transient absorption spectroscopy demonstrating the influence of the carbazole substituents on deactivation from the first excited state in 3 and 4. Protonation of the meso-nitrogen atoms in 3 results in much faster deactivation kinetics from the first excited state. Spectroscopic data were correlated with density functional theory (DFT) and time-dependent DFT calculations on 3 and 4.

A Reusable Eu3+ Complex for Naked‐Eye Discrimination of Methanol from Ethanol with a Ratiometric Fluorimetric Equilibrium in Methanol/Ethanol Mixtures

“…For the previously reported [P 6,6,6,14 ][Eu(NTA) 4 ], when dissolved in protic solvents (e.g., 2-propanol or ethanol) a pronounced interaction between NTAand the solvent was evaluated. [3] The emission spectra agrees with a high symmetry point group for Eu 3+ which breaks down if the compound is dissolved in polar solvents (e.g., n-alcohols).…”

“…[18] This can be explained by the fact that the inclusion of fluorine substituents in the organic ligand, with a high electron-withdrawing effect, reduces the charge density on the oxygen atoms inducing partial dissociation of one of the ligands. The colors used in the scheme (except for NaOPhMe 3 , which is a white powder) are an approximation of the colors of the compounds {[P 6 4 ] compound does not change color when heated. Since this red colored complex is only seven coordinated, we made several attempts to block the reversibility of this process.…”

“…The mechanism behind this proposal is reinforced by the fact that methanol, with a higher coordination ability to Eu 3+ than ethanol, prevents any existing FODin the mixture to coordinate to [Eu(FOD) 3 OPhMe 3 ] -, thus stabilizing the purple color (Figure 3, left). [21] According to ESI-MS data, higher concentrations of [Eu(FOD) 3 OPhMe 3 ] -, and consequently lower concentrations of [P 6,6,6,14 ][Eu(FOD) 4 ] (4.4 % in methanol vs. 1.9 % in ethanol) result in a less effective sensitization mechanism of the Eu 3+ complex and, consequently, a poorer energy transfer with the concomitant establishment of a P-O interaction between the free FODmoiety and the [P 6,6,6,14 ] + cation (Figure 3, right). This explains the ESI-MS result showing the detection of neutral P 6,6,6,14 FOD which is exclusively found in methanol (16.7 % in methanol vs. 0 % found in ethanol, see Table 1).…”

“…In summary, Figure 3 evidences the more intense purple/ pink color of mixture 2 in methanol as the P 6,6,6,14 FOD content is higher. Under UV light, the solutions also have different emission intensities, colors and brightness has the less emissive [Eu(FOD) 3 OPhMe 3 ]moiety is more abundant in methanol and the more emissive [P 6,6,6,14 ][Eu(FOD) 4 ] is more abundant in ethanol. Under UV light, the solutions also have different emission intensities, colors and brightness has the less emissive [Eu(FOD) 3 OPhMe 3 ]moiety is more abundant in methanol and the more emissive [P 6,6,6,14 ][Eu(FOD) 4 ] is more abundant in ethanol.…”

“…[2] We have reported, among other studies, the solvatochromic properties within the [P 6,6,6,14 ][Ln(NTA) 4 ] family (NTA = naphthoyltrifluoroacetonate and [P 6,6,6,14 ] + = trihexyltetradecylphosphonium). Moreover, these two MOFs presented solvatochromism in the presence of diethyl ether vapors.…”