Tert-butyl Zinc Research Articles

Concentration and solvent effects, photochemical and photophysical properties of methyl and tert-butyl zinc(II) and aluminum(III) phthalocyanines

The tetra-methyl and tetra-tert-butyl phthalocyanines were synthesized by cyclotetramerization of phthalonitriles and phthalic anhydride derivatives by traditional and microwave synthesis. Spectroscopic data were obtained for the Zinc(II) and Aluminum(III) derivatives, and solvent effects were investigated in dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), chloroform (CHCl3), methanol (MeOH), and tetrahydrofuran (THF). We have shown that the coordination of the solvent may play a role in the solvent shift. The photophysical and photochemical properties of the studied compounds were investigated in DMSO and DMF. The direct method (analysis of the phosphorescence decay curves of singlet oxygen at 1270 nm) was employed to study singlet oxygen quantum yields. Compounds 6 and 8 showed better results relative to aggregation due to larger substituents and axial ligands. On the other hand, compounds 5 and 7 shown higher singlet oxygen quantum yields because of the central metal ion.

Studying the "Rigid-Flexible" Properties of Polymeric Micelle Core-Forming Segments with a Hydrophobic Phthalocyanine Probe Using NMR and UV Spectroscopy.

The aim of the performed studies was to thoroughly examine the internal structure of self-assembled nanocarriers (i.e., polymeric micelles—PMs) by means of a hydrophobic phthalocyanine probe in order to identify the crucial features that are required to enhance the photoactive probe stability and reactivity. PMs of hydrophilic poly(ethylene glycol) and hydrophobic poly(ε-caprolactone) (PCL) or poly(d,l-lactide) (PDLLA) were fabricated and loaded with tetra tert-butyl zinc(II) phthalocyanine (ZnPc-t-but4), a multifunctional spectroscopic probe with a profound ability to generate singlet oxygen upon irradiation. The presence of subdomains, comprising “rigid” and “flexible” regions, in the studied block copolymers’ micelles as well as their interactions with the probe molecules, were assessed by various high-resolution NMR measurements [e.g., through-space magnetic interactions by the 1D NOE effect, pulsed field gradient spin-echo, and spin–lattice relaxation time (T1) techniques]. The studies of the impact of the core-type microenvironment on the ZnPc-t-but4 photochemical performance also included photobleaching and reactive oxygen species measurements. ZnPc-t-but4 molecules were found to exhibit spatial proximity effects with both (PCL and PDLLA) hydrophobic polymer chains and interact with both subdomains, which are characterized by different rigidities. It was deduced that the interfaces between particular subdomains constitute an optimal host space for probe molecules, especially in the context of photochemical stability, photoactivity (i.e., for significant enhancement of singlet oxygen generation rates), and aggregation prevention. The present contribution proves that the combination of an appropriate probe, high-resolution NMR techniques, and UV–vis spectroscopy enables one to gain complex information about the subtle structure of PMs essential for their application as nanocarriers for photoactive compounds, for example, in photodynamic therapy, nanotheranostics, combination therapy, or photocatalysis, where the micelles constitute the optimal microenvironment for the desired photoreactions.

Host–Guest Superstructures on Graphene-Based Kagome Lattice

The Kagome lattice of iron phthalocyanine (FePc) on the graphene moire pattern is employed as host template for two kinds of guest molecules, FePc and tert-butyl zinc phthalocyanine ((t-Bu)4–ZnPc), to fabricate stable host–guest molecular superstructures. Both FePc and (t-Bu)4–ZnPc molecules prefer to occupy the nanoscale pores of the Kagome lattice. Ordered superstructures with alternate rows of FePc and (t-Bu)4–ZnPc are formed after coadsorption of these two species with a ratio of 1:1 on the Kagome lattice. We elucidate that formation of ordered superstructures of guest FePc and (t-Bu)4–ZnPc are controlled by long-range interaction between the guest molecules mediated by the host Kagome lattice with additional contribution from the graphene/Ru(0001) substrate.

Property study of a new silica nanoparticle delivery system of hydrophobic phthalocyanine using spectroscopic method

Tetra-tert-butyl zinc(II) phthalocyanine has attracted great attention as an effective photosensitizer in the field of photodynamic therapy. However, tetra-tert-butyl zinc(II) phthalocyanine is hydrophobic and trends to aggregate to form the inactive congeries in aqueous solution, which dramatically reduce its photodynamic activity. To solve this problem, tetra- tert-butyl zinc(II) phthalocyanine was encapsulated into silica nanoparticles using microemulsion method and its properties were studied using spectroscopic methods. After embedded inside the silica nanoparticles, the water-solubility, stability and monomer percent of phthalocyanine in water were greatly improved comparing with the free phthalocyanines, and therefore, its photo-induced singlet oxygen generation efficacy of drug-doped silica nanoparticles was improved. The results indicated that encapsulation hydrophobic phthalocyanine into silica nanoparticles was an effective way to solve their problems and promote their clinical application.

High resolution scanning-tunneling-microscopy imaging of individual molecular orbitals by eliminating the effect of surface charge

Ultrathin Iron(II) Phthalocyanine (FePc) monolayers have been employed to decouple individual FePc molecules electronically from the metallic substrate, which allows the intrinsic electronic structure of the free molecule to be preserved and imaged by means of low-temperature scanning tunneling microscopy (STM). High-resolution images reveal the standard “cross” structure for molecules adsorbed at the metal surface, but a detailed electronic structure, corresponding to the highest occupied molecular state (HOMO), for molecules adsorbed at the buffer layer. Different STM images of the molecules in the first and second layer are referred to different interactions between molecules and substrate. This interpretation is verified by control experiments on a second molecule, tetra- tert-butyl zinc Phthalocyanine ((t-Bu) 4ZnPc). We therefore conclude that this effect is generic and can be used to investigate a molecule's electronic structure in detail.

Ultrafast nonlinear optical properties of alkyl phthalocyanines investigated using degenerate four-wave mixing technique

We present our results on the investigation of ultrafast nonlinear optical properties including the time response of 2(3), 9(10), 16(17), 23(24) tetra tert-butyl phthalocyanine (pc1) and 2(3), 9(10), 16(17), 23(24) tetra tert-butyl Zinc phthalocyanine (pc2) studied using degenerate four-wave mixing technique at a wavelength of 800 nm with 100 fs pulses. We recorded large off-resonant second hyperpolarizabilities ( γ) with estimated values of (4.27 ± 0.43) × 10 −31 esu and (4.32 ± 0.43) × 10 −31 esu for pc1 and pc2, respectively, with ultrafast nonlinear optical response in the femtosecond domain. We also estimated the figures of merit for photonic switching applications for both one-photon and three-photon loss mechanisms. The performance of these molecules vis-à-vis other molecules, in general, and phthalocyanines, in particular, is discussed.

Femtosecond and nanosecond nonlinear optical properties of alkyl phthalocyanines studied using Z-scan technique

We report our results on nonlinear optical properties of 2(3), 9(10), 16(17), 23(24) tetra tert-butyl phthalocyanine and 2(3), 9(10), 16(17), 23(24) tetra tert-butyl Zinc phthalocyanine studied using Z-scan technique with 800 nm femtosecond and 532 nm nanosecond pulses. Nonlinear absorption behavior in both femtosecond and nanosecond domains was studied in detail. We observed three-photon absorption with femtosecond laser excitation and strong reverse saturable absorption with nanosecond pulse excitation. We have also evaluated the sign and magnitude of the third-order nonlinearity.

A convergent total synthesis of pumiliotoxins A and B via palladium-catalyzed cross-coupling reaction of homoallylic organozinc compounds with vinyl iodides

A versatile convergent approach for preparing the pumiliotoxin alkaloids has been developed employing a Pd(0)-catalyzed cross-coupling reaction between homoallylic organozincs and vinyl iodides, which led to the asymmetric total synthesis of (+)-pumiliotoxins A ( 1) and B ( 2). The ( Z)-alkylideneindolizidine, which is a common organic part of the organozinc reagents in this approach, was synthesized with a high degree of stereocontrol upon using HfCl 4-mediated addition of the allenylsilane to ( S)-2-acetylpyrrolidine. The ( Z)-iodoalkylideneindolizidine ( 31) thus obtained as an advanced common intermediate was converted into the homoallylzinc chloride derivative 32, which underwent homoallyl-vinyl cross-coupling with the ( E)-vinyl iodide ( 13) using Pd(PPh 3) 4 catalyst to afford the 1,5-diene product 33. Subsequent deprotection provided (+)-pumiliotoxin A. On the other hand, 31 was transformed into the homoallyl- tert-butyl zinc intermediate 39, which was cross-coupled with the ( E)-vinyl iodide ( 36) in the presence of the Pd(0) catalyst. The resulting 1,5-diene product 40 underwent subsequent deprotection to afford (+)-pumiliotoxin B.