The shifts of absorption bands of a few polar molecules have been measured as a function of temperature in several non-polar and polar solvents. These shifts can be described adequately with the Onsager model of dielectrics provided both solute-solvent dipoledipole interactions and dipole-induced-dipole interactions are included.Thermochromic shifts can be used to obtain excited state dipole moments in a way similar to constant temperature solvatochromic shifts; the two methods appear to be in general agreement.

Benzisoxazole 2-oxides are prepared b y the oxidative cyclisation of o-acylphenol oximes, using either lead(iv) acetate or sodium hypochlorite. The scope and limitations of the reaction are discussed.In a recent communication we reported preliminary results on the synthesis of the 1,2-benzisoxazole (indoxazene) 2-oxide system (4). This was effected by oxidative cyclisation of oacylphenol oximes (3) using lead (IV) acetate (Scheme 1). In this paper we present a fuller account of these preparations, and give details of modifications, which in some cases are more convenient than the methods originally applied.

No abstract

intensity of the main line) and is lost in the base line. If a hidden higher binding energy peak were comparable in intensity to that of the lower binding energy peak, then the Ru 3d512 intensity derived from the deconvoluted spectrum shown in Figure 1 would be anomalously low compared with that of other complexes while the C 1s line intensity would be anomalously high. Furthermore, the large Ru 3d splitting required to hide the high-binding-energy Ru 3d peak under the C 1s line ought to be observable even in the Ru 2p3/2 spectrum of the complex. We examined these possibilities by comparing Ru 3d5/2/C1 2p and Ru 2p312/CI 2p intensity ratios recorded for 7 with those of all the other ruthenium chloride complexes. The Ru 3d5/?/C1 2p and Ru 2~~,~/ C l 2p intensity ratios for 7 are both within 20% (albeit on the low side of all but one) of all other measured ratios. The Ru 2p3p line width for 7 is normal. Given experimental errors, we find then that at least 80% of the Ru 3d512 intensity expected from two ruthenium centers in 7 is accounted for in the deconvoluted spectrum. Consequently, the metal XP spectrum of 7 is consistent with that of a strongly delocalized class I11 complex. For such a complex a large portion of the total metal core level photoemission intensity resides in a single, low-binding-energy line. From the quality of the spectrum we estimate, using eq 2, that the electron exchange parameter a for 7 must be greater than 0.9. ConclusionsThe diruthenium complexes examined have provided the opportunity to systematically assess the effects of ligand coordination environment, metal oxidation state, and metal-metal interaction on the metal XP spectra. One complex is of particular interest in this series; the symmetric, mixed-valence [Ru(II),Ru(III)] complex [As(p-tol)3]2C1RuC13RuC1[As(p-tol)3]2. Depending onthe strength of the metal-metal interaction, the metal XP spectrum from this complex could give any results along the continuum from two equally intense metal lines separated by 1 eV or more, to unequal intensities from the two lines with the lower binding energy line "stealing" intensity from the higher binding energy line, to a single, narrow metal line (indistinguishable metal centers). The spectrum observed is a function of the extent of unpaired electron delocalization during photoemission. It was found that, to the degree of resolution possible, this complex gives a metal spectrum in which at least 80% of the metal signal is present in a single, low-binding-energy final state. This experimental result reflects more extensive unpaired electron delocalization in this complex compared with that in the Creutz-Taube complex [(NH3)5Ru(pz)Ru(NH3)5]5+, which gives two well-separated metal lines of equal intensity. We estimate the value of a in 7 is greater than 0.9, whereas in the Creutz-Taube complex it is less than 0.10. This work, combined with Hush's theory, suggests that very unusual metal XP spectra ought to be obtained from class I11 mixed-valence complexes having metal-metal spacings between 3.5 an...

No abstract