Xuebing Leng

Improved silver ion-selective electrodes using novel 1,3-bis(2-benzothiazolyl)thioalkoxy-p-tert-butylcalix[4]arenes

Abstract 1,3-Bis(2-benzothiazolyl)thioalkoxycalix[4]arenes 1 and 2 have been synthesized and found to adopt a cone conformation. Compounds 1 and 4 were characterized by X-ray analysis. Preliminary evaluation of 1 and 2 as ionophores for ion-selective electrodes is reported.

Switching the photoinduced processes in host–guest complexes of β-cyclodextrin-substituted silicon(IV) phthalocyanines and a tetrasulfonated porphyrin

Porphyrins and phthalocyanines are two attractive classes of functional dyes for the construction of artificial light harvesting and charge separation molecular systems. The assembly of these components by supramolecular approach is of particular interest as this provides a facile route to build multi-chromophoric arrays with various architectures and tuneable photophysical properties. We report herein a series of host-guest complexes formed between a tetrasulfonated porphyrin and several silicon(IV) phthalocyanines substituted axially with two permethylated β-cyclodextrin units via different spacers. As shown by electronic absorption and fluorescence spectroscopic methods, the two components bind spontaneously in a 1:1 manner in water with large binding constants in the range of 1.1 × 10(7) to 3.5 × 10(8) M(-1). The photophysical properties of the resulting supramolecular complexes have also been studied in detail using steady-state and time-resolved optical spectroscopic methods. It has been found that two major photoinduced processes, namely fluorescence resonance energy transfer and charge transfer are involved which are controlled by the spacer between the β-cyclodextrin units and the silicon centre of phthalocyanine. Despite the fact that charge transfer is a thermodynamically favourable process for all the complexes, only the ones with a tetraethylene glycol or oxo linker exhibit an efficient charge transfer from the excited phthalocyanine to the porphyrin entity. The lifetimes of the corresponding charge-separated states have been determined to be 200 and 70 ps by picosecond pump-probe experiments.

Synthesis of a tweezer-like bis(arylthiaalkoxy)calix[4]arene as a cation sensor for ion-selective electrodes: an investigation of the influence of neighboring halogen atoms on cation selectivity

Two novel tweezer-like 25,27-dihydroxy-26,28-bis(phenylthiaethoxy)calix[4]arenes 6 and 7 were synthesized by the reaction of 25,27-dihydroxy-26,28-bis(bromoethoxy)calix[4]arenes 3 and 4 for the evaluation of their ion-selectivity in ion-selective electrodes (ISEs). X-ray structural analysis indicated that calix[4]arene 7 is in an interesting infinite linear aggregate via self-inclusion. For investigation of the influences of substitutes on the behavior of the ISEs, the halogen substituted aryl analogues of 25,27-dihydroxy-26,28-bis(arylthiaethoxy)calix[4]arenes 8-12 were also synthesized and their ISE performances were evaluated under the same conditions. ISEs based on 6-12 as neutral ionophores were prepared, and their selectivity coefficients for Ag+ (log KAg,M(pot)) were investigated against other alkali metal, alkaline-earth metal, lead, ammonium ions and some transition metal ions using the fixed interference method (FIM). These ISEs showed excellent Ag+ selectivity over most of the interfering cations examined, except for Hg2+ having relative smaller interference (log KAg,Hg(pot) < or = 2.1). The 19F NMR spectra of 9 and 9.AgClO4 were recorded for investigation the fluorine environments in the complex. The 19F NMR spectra strongly suggested that the fluorine atoms on ionophore 9 participated in ligation with silver cation.

Cu+ and Pt2+ complexes with a p-tert-butylcalix[4]arene fitted with two phosphine pendant arms

Abstract Reaction of 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-bis[{N-(2-diphenyl phosphino)phenyl}carboxyamidemethoxy]calix[4]arene with [Cu(CH3CN)4]ClO4 and Pt(COD)Cl2 gave two new complexes (1 and 2, respectively). Their structures were determined by X-ray analysis. Complex 1 has two seven-membered metallo-cycles and complex 2 has one five-membered metallo-cycle.

Novel bis(phenylselenoalkoxy)calix[4]arene molecular tweezer receptors as sensors for ion-selective electrodes

Four tweezer-like 25,27-dihydroxy-26,28-bis(phenylselenoalkoxy)-5,11,17,23-tetra-tert-butylcalix[4]arenes 5–8 were synthesized for the evaluation of their ion-selectivity in ion-selective electrodes (ISEs). For investigation of the influences of the coordinate atoms on the ion-selectivity, 25,27-dihydroxy-26,28-bis(alkylthiaalkoxy)-5,11,17,23-tetra-tert-butylcalix[4]arenes 9–11 were also prepared and characterized. On the other hand, 1,3-bis(phenylseleno)propane 12 was synthesized for comparison of the influences of coordinate patterns of different ionophores on the ion-selectivity of ISEs. ISEs based on 5–12 as neutral ionophores were prepared, and their selectivity coefficients for Ag+ (log KpotAg,M) were investigated against alkali metal, alkaline-earth metal, lead, and ammonium ions and some transition metal ions using the fixed interference method (FIM). These ISEs showed excellent Ag+ selectivity over most of the interfering cations examined, except for Hg2+, which had relatively smaller interference (log KpotAg,Hg ≤ −1.6).

Preparation and photophysical properties of a tetraethylene glycol-linked phthalocyanine–porphyrin dyad and triad

Treatment of 1,4-bis(tetraethylene glycol)-substituted zinc(II) phthalocyanine with p-toluenesulfonyl chloride and triethylamine followed by 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin and K2CO3 resulted in the formation of both a covalently linked phthalocyanine–porphyrin dyad and triad. The photophysical properties of these hetero-arrays were studied in detail using steady-state and time-resolved spectroscopic methods. Upon excitation at the porphyrin moiety, both compounds exhibited predominantly highly efficient excitation energy transfer from the excited porphyrin to the phthalocyanine core. The rate of energy transfer (2.4 × 1010 s−1) was more than 20-fold faster than the rate of electron transfer (1.1 × 109 s−1). When the phthalocyanine core of the dyad and triad was excited either directly or via excitation energy transfer, its singlet excited state underwent charge transfer leading to reduction in the fluorescence quantum yield and fluorescence lifetime. The rate of charge transfer for the triad (2.8 × 108 s−1) was about two-fold higher than that for the dyad (1.5 × 108 s−1) due to the presence of an additional porphyrin moiety in the triad.

Heterobimetallic Pt(II)-M(I) (M = Cu, Ag) eight-membered macrocyclic complexes with large-bite P, N-ligand bridges

Reaction of a new large-bite P,N-ligand, 2-(N-diphenylphosphinomethyl-N-benzyl)aminopyridine (1) with (COD)PtCl2 and (COD)Pt(CCPh)2 give cis-(L)2PtCl2 (2) and trans-(L)2Pt(CCPh)2 (3), respectively. Complex 3 reacted with M(I) (M = Cu, Ag) perchlorate using its pyridyl and alkynyl groups to afford a novel type of mixed-metal macrocyclic complexes PtM2(L)2(CCPh)2(ClO4)2 (M = Cu, 4; M = Ag, 5). Complex 4 can be converted to the solvated complexes Pt[Cu(solvent)]2(μ-L)2(CCPh)2(ClO4)2 (solvent = H2O, 4; CH3CN, 4″) by recrystallization of 4 in the corresponding solvents. The crystal structures of complexes 2, 3, 4 and 4″·CH2Cl2 and luminescence properties of 3, 4 and 5 have been determined.

{[N‐Benzyl‐N‐(2‐pyridyl)­amino]­methyl­ene}di­phenyl­phosphine oxide

The title compound, Ph2P(O)CH2N(CH2Ph)C5H4N or C25H23N2OP, was obtained by reaction of Ph2PCH2N(CH2Ph)C5H4N and H2O2. The crystal structure shows distorted tetrahedral geometry around the P atom.