Electrochemical and spectroelectrochemical properties of novel lutetium(III) mono- and bis-phthalocyanines

Novel non-peripheral mercaptopyridine-substituted mono- and double-decker lutetium(III) phthalocyanines: synthesis, photophysicochemical and electrochemical properties

In this study, novel non-peripheral tetra-mercaptopyridine-substituted mono- and double-decker phthalocyanines (LuPc and LuPc2) containing lutetium(III) as a rare earth metal were synthesized and characterized using different spectroscopic techniques. ESR and electrochemical analyses were performed to support the sandwich structure of LuPc2. The g factor was determined to be 2.00039 and the characteristic first reduction couple at 0.29 V indicated a reduction of the radical Pc ring of LuPc2. In addition, the UV-Vis-NIR spectra of LuPc2 in neutral, reduced, and oxidized states demonstrate its intrinsic π-radical nature in CHCl3. The photophysicochemical properties of LuPc and LuPc2 were investigated in DMSO. It was found that mono-phthalocyanine (LuPc) is a more effective photosensitizer than double-decker (LuPc2) and metal-free (H2Pc) phthalocyanines based on a comparison of their photophysical and photochemical properties. The singlet oxygen quantum yields (ΦΔ) of the synthesized LuPc and LuPc2 compounds were calculated to be 0.57 and 0.14, respectively, and the obtained results were compared with H2Pc (ΦΔ = 0.04). Also, electrochemical measurements were performed to estimate their redox potentials and the results indicated the important electrochemical performance of double-decker phthalocyanine (LuPc2).

Octopus-Type Crown-Bisphthalocyaninate Anchor for Bottom-Up Assembly of Supramolecular Bilayers with Expanded Redox-Switching Capability

Achievement of information storage at molecular level remains a pressing task in miniaturization of computing technology. One of the promising approaches for its practical realization is development of nanoscale molecular switching materials including redox-active systems. The present work demonstrates a concept of expansion of a number of available redox-states of self-assembled monolayers through supramolecular approach. For this, the authors synthesized an octopus-like heteroleptic terbium(III) bisphthalocyaninate bearing one ligand with eight thioacetate-terminated "tentacles" (octopus-Pc) and a ligand with four crown-ether moieties (H₂ [(15C5)₄ Pc]). It is shown that octopus-Pc forms stable monolayers on gold, where its face-on orientation allows for subsequent binding of crown-phthalocyanine molecules via potassium ion bridges. This chemistry is utilized to form a heterogeneous bilayer, in which a single molecule thick adlayer brings an additional redox-state to the system, thus expanding the multistability of the system as a whole. All four redox states available to this system exhibit characteristic absorbance in visible range, allowing for the switching to be easily read out using optical density measurements. The proposed approach can be used in wide range of switchable materials-single-molecule magnets, conductive, and optical devices, etc.

Synthesizing and evaluating the photodynamic efficacy of asymmetric heteroleptic A7B type novel lanthanide bis-phthalocyanine complexes

In this study heteroleptic A₇B type novel Lu(iii) and Eu(iii) lanthanide phthalocyanines (LnPc(Pox)[Pc′(AB₃SH)]) with high extinction coefficients have been synthesized as candidate photosensitizers with reaction yields higher than 33%. The singlet oxygen quantum yields of LuPc(Pox)[Pc′(AB₃SH)] and EuPc(Pox)[Pc′(AB₃SH)], respectively, were measured 17% and 1.4% by the direct method in THF. The singlet oxygen quantum yield of LuPc(Pox)[Pc′(AB₃SH)] in THF is the highest among lutetium(iii) bis-phthalocyanine complexes to date. The photodynamic efficacy of the heteroleptic lanthanide phthalocyanines was evaluated by measuring cell viabilities of A549 and BEAS-2B lung cells, selected to representing in vitro models for testing cancer and normal cells against potential drugs. The cell viabilities demonstrated concentration dependent behavior and were varied by the type of phthalocyanines complexes. Irradiation of the cells for 30 minutes with LED array at 660 nm producing flux of 0.036 J cm⁻² s⁻¹ increased cell death for LuPcPox-OAc, LuPc(Pox)[Pc′(AB₃SH)] and ZnPc. The IC₅₀ concentrations of LuPc(Pox)[Pc′(AB₃SH)] and ZnPc were determined to be below 10 nM for both cell lines, agreeing very well with the singlet oxygen quantum yield measurements. These findings suggest that LuPc(Pox)[Pc′(AB₃SH)] and particularly LuPcPox-OAc are promising drug candidates enabling lowered dose and shorter irradiation time for photodynamic therapy.

Novel bis-lanthanide Lu(iii) and Eu(iii) phthalocyanine complexes have been designed/synthesized and tested their photodynamic efficacy for A549 and BEAS-2B cells in vitro conditions as candidate photosensitizers in PDT.

Phthalocyanine-polyoxotungstate lanthanide double deckers

Two archetypal tetradentate ligands with square donor patterns, namely phthalocyanate and monolacunary Keggin-type polyoxotungstate, coordinate to rare earth ions to yield C_s-symmetric heteroleptic double-decker complexes.

Tetra- and Octa-[4-(Thiophen-3-Yl)Phenoxy]-Bearing Metal-Free and Lu(III) Phthalocyanines: Synthesis, Characterisation and Investigation of Photophysical Properties

4-[4-(Thiophen-3-yl)phenoxy]phthalonitrile and 4,5-bis[4-(thiophen-3-yl)phenoxy]phthalonitrile and their corresponding tetra- and octa-substituted metal-free and Lu(III) phthalocyanine derivatives have been synthesised. The aggregation behaviour of the phthalocyanine compounds has been investigated in different solvents and concentrations and the effects of the substituent and the lutetium on their photophysical properties are reported.

Enhanced electrochromic properties of a polypyrrole–indigo carmine–gold nanoparticles nanocomposite

Enhanced electrochromic properties of a PPy–IC–Au_nanop nanocomposite obtained by the one-step growth of gold nanoparticles and electropolymerization of indigo carmine doped polypyrrole.