pH-Sensitive subphthalocyanines and subazaphthalocyanines

Although subphthalocyanines (SubPcs) possess advantageous fluorescence properties and serve as an amazing tool to attach a recognition sensor moiety to the axial position, a limited number of switchable SubPcs have been described so far. Isosteric aza-replacement is known to improve sensing properties in closely related phthalocyanine families; however, pyrazino[2,3-b,g,l]subporphyrazines (SubPyzPzs) have not yet been investigated for use in sensing applications. Therefore, this project focuses on the synthesis and sensing abilities of pH-sensitive SubPcs and SubPyzPzs on the principle of photoinduced electron transfer (PET). 4-Dimethylaminophenoxy (for acidic pH) or 4-hydroxyphenoxy (for basic pH) groups were employed as pH-sensitive axial ligands. Electrochemical studies revealed improvements in the electron-accepting properties of SubPyzPzs (E_red-0.56 V vs. SCE) in comparison to those of SubPcs (E_red-1.0 V vs. SCE). Hydroxy groups on the axial phenoxy ligands of SybPyzPzs and SubPcs have been found to act as donors for PET. The sensing properties under basic conditions could not be studied, since all the SubPcs and SubPyzPzs decomposed under basic conditions, SubPyzPzs were more susceptible to this process. On the other hand, compounds with 4-dimethylaminophenoxy groups as axial ligands showed great potential for sensing applications. These compounds were nonfluorescent (Φ_F < 0.01) in acetone due to efficient PET, while their fluorescence steeply increased by two orders of magnitude upon the addition of trifluoroacetic acid, reaching a Φ_F value of up to 0.17 (λ_em range of 563-590 nm). These compounds maintained their sensing properties in aqueous medium after incorporation into microemulsions. The most basic derivative showed pK_A = 2.95 with Φ_F = 0.10 in the ON state (fluorescence enhancement factor = 46, λ_em = 577 nm).

A new bio-compatible Cd2+-selective nanostructured fluorescent imprinted polymer for cadmium ion sensing in aqueous media and its application in bio imaging in Vero cells

Schematic representation of Cd²⁺ recognition by the imprinted polymer and fluorescence signal creation as a result of the mentioned recognition process.

A small molecular boron-phenylpyrrin sensor for H+/Fe3+ and its application as a digital demultiplexer

A julolidine-based boron-phenylpyrrin small molecule has been designed and synthesized through a one-pot condensation-complexation procedure. Systematic optical studies show that this compound displays two distinct optical responses to the addition of HCl and Fe[Formula: see text] in succession: the addition of HCl induces an obvious red shift in its maximum absorption and fluorescence emission bands accompanied with the fluorescence quenching, whereas after synchronously adding H[Formula: see text] and Fe[Formula: see text], the maximum absorption and fluorescence emission wavelength were found to shift little but with an obvious decrease in the absorbance and fluorescence intensity, suggesting the dual-detecting nature of this compound to H[Formula: see text] and Fe[Formula: see text] under acid conditions. More interestingly, based on the HCl/Fe[Formula: see text]-mediated absorption and fluorescence signal features, JBPP can function as AND, NAND, INH and IMP logic gates which can be further developed into a 2:4 digital demultiplexer These will endow this small molecule compound with great potential for applications in molecular logic material, chemosensors and biological fields.

Structural factors influencing the intramolecular charge transfer and photoinduced electron transfer in tetrapyrazinoporphyrazines

A series of unsymmetrical tetrapyrazinoporphyrazines (TPyzPzs) from the group of azaphthalocyanines with one peripherally attached amino substituent (donor) were synthesized, and their photophysical properties (fluorescence quantum yield and singlet oxygen quantum yield) were determined. The synthesized TPyzPzs were expected to undergo intramolecular charge transfer (ICT) as the main pathway for deactivating their excited states. Several structural factors were found to play a critical role in ICT efficiency. The substituent in the ortho position to the donor center significantly influences the ICT, with tert-butylsulfanyl and butoxy substituents inducing the strongest ICTs, whereas chloro, methyl, phenyl, and hydrogen substituents in this position reduce the efficiency. The strength of the donor positively influences the ICT efficiency and correlates well with the oxidation potential of the amines used as the substituents on the TPyzPz as follows: n-butylamine < N,N-diethylamine < aniline < phenothiazine. The ICT (with conjugated donors and acceptors) in the TPyzPz also proved to be much stronger than a photoinduced electron transfer in which the donor and the acceptor are connected through an aliphatic linker.

Theoretical study on phthalocynine-Fe(II)-based fluorescent sensors for cyanide anion

Three fluorescent sensors bearing phthalocynine- Fe ( II ) moiety were designed specifically for detecting cyanide anions, and investigated by DFT/TDDFT method. Comparison of the geometrical and photophysical properties of these sensor molecules, equipped with H -, carbamoyl and phthalimino groups, provided a deep insight into the sensor–cyanide interactions. The binding energy calculation shows that all the three sensors have good selectivity to the cyanide anion. Especially, frontier molecular orbital analysis confirmed that there was a photoinduced electron transfer (PET) process in the sensor with phthalimino group upon the addition of cyanide anion. This process could cause the fluorescence change. As a result, the sensor with phthalimino group displayed several favorable sensing properties.

Zinc phthalocyanines with fluorinated substituents for direct sensing of carbamate and organophosphate pesticides in water

Water pollution by pesticides as the result of intensive agriculture and horticulture has brought many negative consequences to humans and ecosystems. Among others, chemical sensor systems are under intense development for direct pesticide analysis in aqueous samples as a cost effective and simple alternative analytical method. In this work, a set of zinc phthalocyanines is studied in its liquid sensing properties using quartz crystal microbalances. Four different species selected from the two most common organophosphorus and carbamate classes of pesticides are used as test analytes. The phthalocyanines are chemically modified with different fluorinated substituents to increase sensor sensitivity and govern pesticide selectivity in order to create sensors with widely diverging analyte responses. By this means, sensors with a general high sensitivity and selectivity for the two pesticide classes were obtained and detection limits down to 0.03 mg.L-1 could be achieved. The response data of the sensors are analyzed in detail using exploratory multivariate data evaluation methods. The results show that phthalocyanine based sensors are a truly capable platform for chemical analysis systems of aqueous samples.