A3B-Type Phthalocyanine-Based Homoleptic Lanthanide(III) Double-Decker π-Radical Complexes Bearing Functional Hydroxy Groups: Synthetic Approach, Spectral Properties and Electrochemical Study

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).

Synthesis and Dynamic Behavior of Ce(IV) Double-Decker Complexes of Sterically Hindered Phthalocyanines

Phthalocyanines and their double-decker complexes are interesting in designing rotative molecular machines, which are crucial for the development of molecular motors and gears. This study explores the design and synthesis of three bulky phthalocyanine ligands functionalized at the α-positions with phenothiazine or carbazole fragments, aiming to investigate dynamic rotational motions in these sterically hindered molecular complexes. Homoleptic and heteroleptic double-decker complexes were synthesized through the complexation of these ligands with Ce(IV). Notably, CeIV(Pc2)2 and CeIV(Pc3)2, both homoleptic complexes, exhibited blocked rotational motions even at high temperatures. The heteroleptic CeIV(Pc)(Pc3) complex, designed to lower symmetry, demonstrated switchable rotation along the pseudo-C4 symmetry axis upon heating the solution. Variable-temperature 1H-NMR studies revealed distinct dynamic behaviors in these complexes. This study provides insights into the rotational dynamics of sterically hindered double-decker complexes, paving the way for their use in the field of rotative molecular machines.

Rare-earth based tetrapyrrolic sandwiches: chemistry, materials and applications

This review summarises advances in chemistry of tetrapyrrole sandwiches with rare earth elements and highlights the current state of their use in single-molecule magnetism, organic field-effect transistors, conducting materials and nonlinear optics.

Lanthanide-tetrapyrrole complexes: synthesis, redox chemistry, photophysical properties, and photonic applications

Tetrapyrrole derivatives such as porphyrins, phthalocyanines, naphthalocyanines, and porpholactones, are highly stable macrocyclic compounds that play important roles in many phenomena linked to the development of life. Their complexes with lanthanides are known for more than 60 years and present breath-taking properties such as a range of easily accessible redox states leading to photo- and electro-chromism, paramagnetism, large non-linear optical parameters, and remarkable light emission in the visible and near-infrared (NIR) ranges. They are at the centre of many applications with an increasing focus on their ability to generate singlet oxygen for photodynamic therapy coupled with bioimaging and biosensing properties. This review first describes the synthetic paths leading to lanthanide-tetrapyrrole complexes together with their structures. The initial synthetic protocols were plagued by low yields and long reaction times; they have now been replaced with much more efficient and faster routes, thanks to the stunning advances in synthetic organic chemistry, so that quite complex multinuclear edifices are presently routinely obtained. Aspects such as redox properties, sensitization of NIR-emitting lanthanide ions, and non-linear optical properties are then presented. The spectacular improvements in the quantum yield and brightness of Yb^III-containing tetrapyrrole complexes achieved in the past five years are representative of the vitality of the field and open welcome opportunities for the bio-applications described in the last section. Perspectives for the field are vast and exciting as new derivatizations of the macrocycles may lead to sensitization of other Ln^III NIR-emitting ions with luminescence in the NIR-II and NIR-III biological windows, while conjugation with peptides and aptamers opens the way for lanthanide-tetrapyrrole theranostics.

Synthesis and characterization of heteroleptic rare earth double-decker complexes involving tetradiazepinoporphyrazine and phthalocyanine macrocycles

Reaction of (2,3,9,10,16,17,23,24-octabutylphthalocyaninato)lanthanide(iii) acetylacetonates (BuPcLn(acac), 1a-c, Ln = Lu (a), Eu (b), La (c)) with a tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazine ligand (tBuPhDzPzH2, 2) produced sandwich compounds (tBuPhDzPz)Ln(BuPc) (3a-c), which represent the first heteroleptic double-deckers incorporating both Pc and DzPz decks. A combination of high-resolution mass spectrometry, UV-Vis/NIR, MCD, and 1H NMR spectroscopy, and square-wave voltammetry provided unambiguous characterization of target complexes 3 indicating that their spectral and electrochemical properties are generally intermediate with respect to their homoleptic relatives. Based on the data of solution-state 1H-1H NMR (COSY, NOESY) correlation spectroscopy supported by DFT calculations, a dimerization tendency of compounds 3 proportional to the Ln(iii) ion size was found. The spectroelectrochemical study of 3 and the corresponding homoleptic double-deckers revealed a pronounced tendency to aggregation of the one-electron oxidized forms of DzPz-containing double-decker complexes compared to homoleptic Pc2Ln compounds.

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.

Optical readout of controlled monomer-dimer self-assembly

5,7-Substituted 1,4-diazepinoporphyrazine magnesium(ii) complexes were synthesized via Mg(ii)-alkoxide templated macrocyclization. A single crystal growth synchrotron diffraction analysis permitted what is to our knowledge the first structural characterization of a 1,4-diazepinoporphyrazine. It exists as a dimer in the solid state. In silico calculations supported by solution phase spectral studies involving a series of representative derivatives, provided insights into the factors governing dimerization of 1,4-diazepinoporphyrazines. The present 1,4-diazepinoporphyrazines serve as useful probes for understanding the determinants that guide dimer-monomer equilibria and the self-assembly of phthalocyanine derivatives.

Self-Assembly of TbPc2 Single-Molecule Magnets on Surface through Multiple Hydrogen Bonding

The complexation between 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (NaPy) is used to promote the mild chemisorption of a UPy-functionalized terbium(III) double decker system on a silicon surface. The adopted strategy allows the single-molecule magnet behavior of the system to be maintained unaltered on the surface.

The effect of the cobalt and manganese central metal ions on the nonlinear optical properties of tetra(4-propargyloxyphenoxy)phthalocyanines

The phthalocyanines were investigated as optical limiters. The paramagnetic complexes were not effective owing to quenching of the excited states.

Formation of TbPc2 Single-Molecule Magnets' Covalent 1D Structures via Acyclic Diene Metathesis

We present here a reaction scheme to connect TbPc₂ single-molecule magnets into 1D architectures using acyclic diene metathesis. To investigate the impact of the bonding through aliphatic chains on the magnetic properties of TbPc₂, we isolate and characterize the dimeric species obtained as one of the products of the reaction. Remarkably, the magnetic properties are only slightly modified after the formation of the bond between molecules, enlightening the great potential of this reaction scheme.

Highly soluble tetrasubstituted lanthanide bis-phthalocyanines; synthesis, characterization, electrical properties and aggregation studies

We report the synthesis, characterization and electrical properties of lanthanide metal based bis-phthalocyanines, {M[Pc-(β-HHT)4]2} (HHT:1-hydroxyhexane-3-ylthio){ M [Formula: see text] Lu[Formula: see text] (2), Eu[Formula: see text] (3), and Yb[Formula: see text] (4)}. The interaction of bis-phthalocyanines with Ag[Formula: see text] and Pd[Formula: see text] metal ions were investigated by UV-vis spectroscopy and atomic force microscopy. Thin films of bis-phthalocyanine molecules were prepared by spin-coating method. The surface morphology of thin films were performed with Atomic Force Microscopy as further investigate. The electrical transport properties of ITO/Pc/Al devices were investigated. At low voltages all the films showed an ohmic conduction, whereas at higher voltage levels the conduction is dominated by space charged limited conduction with exponential distribution of trapping levels. Measurements of current density as a function of inverse temperature at constant applied voltage yielded a hole mobility values, μp[Formula: see text], [Formula: see text] and [Formula: see text] m2.sn[Formula: see text].V[Formula: see text] for lanthanium phthalocyanines. From the analysis of frequency, ω, dependence of electrical conductivity, σac. it was found that the [Formula: see text] obeys the power law given by σac = Aωs, in which the frequency exponent “s” decreases with temperature.

Double-decker bis(tetradiazepinoporphyrazinato) rare earth complexes: crucial role of intramolecular hydrogen bonding

Study focuses on specific interactions in diazepine-containing macroheterocycles.

Thermally stable J-type phthalocyanine dimers as new non-linear absorbers for low-threshold optical limiters

The possibility of developing new advanced optical limiters of laser radiation at 532 nm with low limiting thresholds has been demonstrated on thermally stable phthalocyanine J-type dimeric complexes of Mg, Zn, Cu, Ni, and Co.

Peripheral functionalisation of a stable phthalocyanine J-type dimer to control the aggregation behaviour and NLO properties: UV-Vis, fluorescence, DFT, TDHF and thermal study

Chemical modification of a stable phthalocyanine J-type dimer was demonstrated for the first time, with an emphasis on controlling the aggregation, spectral and NLO properties.

meso-Phenyltetrabenzotriazaporphyrin based double-decker lanthanide(iii) complexes: synthesis, structure, spectral properties and electrochemistry

A series of tetrabenzotriazaporphyrin half-sandwich and sandwich compounds, including unexpected meso-dearylated derivatives as well as the first triple-decker, have been prepared.

Synthesis of phthalocyanine compounds bearing 2-(diethoxyphosphoryl)-4-methylpenta-1,3-dienyl functional groups

Free-base phthalocyanine ligands and their zinc derivatives representing functionally monosubstituted (A3B type) or tetrasubstituted (A4 type) compounds with 2-diethoxyphosphoryl-4-methylpenta-1,3-dienyl moieties have been synthesized for the first time. Their structures were characterized by MALDI-TOF mass-spectrometry as well as 1 H and 31 P NMR spectroscopy data. A tendency to aggregation in dependence on the nature of the solvent was demonstrated as well.

MALDI-TOFMS analysis of coordination and organometallic complexes: a nic(h)e area to work in

A mini-review of the characterisation of metal-containing compounds by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS) is presented. Organometallic and coordination compounds have many varied applications, most notably in industrial catalytic processes and also in the electronics and healthcare sectors. In general, the compounds discussed, be they small or large molecules, have a high percentage metal content, rather than simply containing 'a metal atom'. A brief history of the field is given, but the main scope over the last 5 years is covered in some detail. How MALDI-TOFMS compliments electrospray for metal-containing compounds is highlighted. Perspectives on recent advances, such as solvent-free and air/moisture-sensitive sample preparation, and potential future challenges and developments, such as nanomaterials and metallodrug/metallometabolite imaging, are given.