Protophane und Polyaromaten, XXVII. Fragmentierungen bei der Massenspektrometrie von Heteropolyaromaten, neue Beispiele für den massenspektrometrischen ortho ‐Effekt

Abstract

Heteropolyaromaten, bei denen die nichtterminalen Aromateneinheiten jeweils mit zwei orthostandigen aromatischen Kettengliedern verkniipft sind (2a -e, 3a, b, 4a -e, 5a -c, 8), erleiden im Massenspektrometer in hohem Mane Spaltung zwischen den Aromateneinheiten. Hierfiir wird ein Additions-Eliminierungs-Mechanismus postuliert , der zur Ausbildung eines neuen sechsgliedrigen Ringes im kationischen Fragment fiihrt und durch eine spiralige Sekundarstruktur der Polyaromaten begiinstigt ist. -Die Synthese von sechs Heterotetraaromaten (2a -e, 3a) wird beschrieben. Protophanes and Polyaromatics, XXVII l) Fragmentation in the Mass Spectrometry of Heteropolyaromatics; New Examples of the Mass Spectrometric ortho-EffectHeteropolyaromatics, the nonterminal aromatic units of which are connected in ortho-position with other aromatic members of the chain (2a-e, 3a, b, 4a-e, 5 a -c , 8), suffer in the mass spectrometer fission between the aromatic units in high degree. An addition-elimination mechanism is postulated which brings about a new six-membered ring in the cationic fragment and is favored by a helical secondary structure of the polyaromatics. -The synthesis of six heterotetraaromatics (2a-e, 3a) is described.In den Massenspektren (70 eV) von Heteropolyaromaten werden Fragment-Ionen, die durch Sprengung der Bindungen zwischen den Ringen entstehen, nach unseren Er-

Cyclometalated Complexes of Palladium(II) and Platinum(II): cis-Configured Homoleptic and Heteroleptic Compounds with Aromatic C⌒N Ligands

“…Yield: 17% of orange plates. MS m/z (relative intensity): 416 (14), 418 (20), 420 (M + ) 40), 422 (35), 424 (23), 426 (20), 428 (17) X-ray Crystal Structure Analyses. Crystal data and details of structure refinement for complexes 1 and 3 are given in Table 1.…”

Photoinduced energy‐transfer in covalently and non‐covalently linked supramolecular arrays of metal polypyridyl complexes

“…Seeking to develop a one-step synthesis of the ligand we attempted to exploit the known propensity of pyridine radical anions to couple symmetrically as the C 4 position. Thus treatment of pyridine with LDA (lithium diisopropylamide) affords 4, 4 -dihydro-4, 4 -bipyridine, which is readily oxidised to 4, 4 -bipyridine [8]; similarly, coupling of 3, 3 -bipyridine in this way affords 3, 3 : 4 , 4 : 3 , 3 -quaterpyridine via symmetrical dimerisation at the C 4 position [9]. We reasoned that treatment of 2, 2 -bipyridine with LDA would therefore afford the symmetric 2, 2 : 4 , 4 : 2 , 2 -quaterpyridine.…”