<div>Due to the great potential expressed by an anticancer drug candidate previously reported by our group, namely Ru-sq ([Ru(DIP)2(sq)](PF6) (DIP: 4,7-diphenyl-1,10-phenanthroline, sq: semiquinonate ligand), we describe in this work a structure-activity relationship (SAR) that involves a broader range of derivatives resulting from the coordination of different catecholate-like dioxoligands to the same Ru(DIP)2 core. More in detail, we chose catechols carrying either electron-donating or electronwithdrawing groups EDG or EWG and investigated the physico-chemical and biological properties of their complexes. Several pieces of experimental evidences demonstrated that the coordination of catechols bearing EDGs led to deep red positively charged complexes 1–4 in which the preferred oxidation state of the dioxoligand is the uninegatively charged semiquinonate. Complexes 5 and 6, on the other hand, are blue/violet neutral complexes which carry an EWG substituted dinegatively charged catecholate ligand. The biological investigation of complexes 1–6 led to the conclusion that the difference in their physico-chemical properties has a strong impact on their biological activity. Thus, complexes 1–4 expressed much higher cytotoxicities than complexes 5 and 6. Complex 1 constitutes the most promising compound of the series and was selected for a more in-depth biological investigation. Apart from its remarkably high cytotoxicity (IC50 = 0.07–0.7 μM in different cancerous cell lines) complex 1 was taken up by HeLa cells very efficiently by a passive transportation mechanism. Moreover, its moderate accumulation in several cellular compartments (i.e. nucleus, lysosomes, mitochondria and cytoplasm) is extremely advantageous in the search of a potential drug with multiple modes of action. Further DNA metalation and metabolic studies pointed to the direct interaction of complex 1 with DNA and to the severe impairment of the mitochondrial function. Multiple targets, together with its outstanding cytotoxicity, make complex 1 a valuable candidate in the field of chemotherapy research.</div>

Upon oxidation to the radical cation, the eight-membered ring in dibenzo[a,e]cyclooctene (2) seems to retain its tub-shaped geometry; in this regard, 2 resembles the parent cyclooctatetraene 1.Cyclooctatetraene 1 has a tub-shaped carbon framework,l whereas in both the dianion 12-and the radical anion 1.-the n-perimeter appears to be flattened.2 The coupling constant, ( U H ( 0.321 mT, of eight equivalent ring protons in 1.-is fully consistent with the planar geometry. In contrast, the radical

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Dedicated to Prof. Edgar Heilhronner on the occasion of his 70th birthday (4.11.91) Reduction of tribenzo[a,c,e]cyclooctene (2) and its 2,3-and 1,4-dimethyl derivatives (4 and 5 ) , as well as of l,l-dimethyl-l0,11-propane-2,2-diylidene-lH-benzo[5,6]cycloocta[ 1,2,3,4-deflfluorene (6) and its 5,6-didehydro derivative (7) was followed by cyclic voltammetry. The radical anions of these compounds and those of their derivatives (D)2, (D)5, and (D)6, deuterated at C(9) in 2 and 5 or in the corresponding position of 6, have been characterized with the use of ESR, ENDOR, and TRIPLE-resonance spectroscopy. The cyclic-voltammetic and proton-hyperfine data are consistent with the increasing deviations of the radical anions from planarity in the order 6:,

Baeyer-Villiger oxidation of 10 utilizing trifluoroperacetic acid gave the acetate 11 which reacted with methyllithium to give 4-hydroxy-iránj:-bicyclo[5.1.0]octane (12) in 64% yield based on 10.