The water-soluble titanium(iv)-porphyrin complex, oxo[5,10,15,20-tetra(4-pyridyI)porphyrinato]titanium(iv) [TiO(tpypH4)4+], was found to enhance the spectrophotometric determination of trace amounts of hydrogen peroxide. A 0.05 rnol dm-3 hydrochloric acid solution containing TiO(tpypH4)4+ was used (the Ti-TPyP reagent), the absorbance of which decreased at 432 nm as hydrogen peroxide was added. This was due to the consumption of the TiO(tpypH4)4+ complex following the formation of peroxo [5,10,15,20tetra(4-pyridyl)porphyrinato]titanium(iv). The decrease in absorbance at 432 nm (AA432) was proportional to the concentration of hydrogen peroxide, from 1 .O x 10-8 to 2.8 x 10-6 rnol dm-3, in the sample solution (25 pmol-7.0 nmol per assay). The reaction was accelerated by hydrogen ions; the presence of 1.6 rnol dm-3 perchloric acid was found to promote complexation to the greatest extent. A AA432 of 1.9 x ' 105 was found for 1 rnol dm-3 hydrogen peroxide. A measurement precision of 1.2% for 1.0 x 10-6 rnol dm-3 hydrogen peroxide ( n = 8 ) was obtained. The reagent can be used for the determination of hydrogen peroxide in water samples such as tap water and rainwater over the range from 1.05 x 10-7 to 3.34 x 10-5 rnol dm-3.

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Bis(bicyclic) molecules dimethanochrysene and diethanochrysene were prepared by Diels‐Alder reaction of the naphthodiyne equivalent with cyclopentadiene and 1,3‐cyclohexadiene, respectively. Reaction of dimethanochrysene and 7,9‐diphenyl‐8H‐cyclopent[a]acenaphthylen‐8‐one resulted in the generation of a fluorescent hydrocarbon in unexpected multistep pericyclic reactions. Syn‐oriented diethanochrysene‐connected bisporphyrin tweezers was prepared from the reaction of chrysene‐bridged syn‐dipyrrole with tripyrranedicarbaldehyde. The structure of the receptor and its 1 : 1 complex with C60 or C70 was determined by X‐ray diffraction analysis. The dihedral angles of the bicyclo[2.2.2]octadiene moieties were narrowed by complexation of the receptor with the fullerenes. The binding affinities of the tweezers with C60 and C70 were calculated to be 2.7(4)×104 and 8.01(7)×104 M−1, respectively by UV‐vis and fluorescence spectroscopy.

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