960590-82-3Relevant academic research and scientific papers
Pentanuclear Heterometallic String Complexes with High-Bond-order Units [Ni2 3+?Mo2 4+?Ni2+(bna)4X2]3+ (X = Cl, NCS)
Hsu, Ssu-Chieh,Lin, Geng-Min,Lee, Gene-Hsiang,Chen, Chun-Hsien,Peng, Shie-Ming
, p. 122 - 132 (2018)
Our quest for ligands toward the synthesis of functional metal string complexes started from α-pyridylamido anions. With the modulation of naphthyridylamido anions, the ligands carry less negative charge to be balanced and, thus, to some extent, can tune the oxidation state of the metal centers and the strength of metal–metal interactions. For example, the formation of Ni2 3+, a mixed-valence moiety, has been demonstrated. In this paper, high-bond-order units of M2 (Mo2 or Ru2) and Ni2 3+ are introduced and supported by four equatorial ligands of the bisnaphthyridylamido anion (bna?). The resulting compounds are [Ni2Mo2Ni(bna)4Cl2](PF6)3 (1), [Ni2Mo2Ni(bna)4(NCS)2](PF6)3 (2), and [Ni2Ru2Ni(bna)4Cl2](ClO4)3 (3). X-ray crystallography reveal quadruply bonded characteristics with Mo–Mo distances of 2.133(2) and 2.109(2) ? for 1 and 2, respectively. The Ni2 moieties have a short Ni–Ni distance of 2.331(5) for 1 and 2.334(4) ? for 2, suggesting the formation of mixed-valence Ni2 3+ units. It appears that there are no significant metal–metal interactions between Mo2 and its neighboring Ni centers. Characterization using magnetism, voltammetry, electronic absorption, and single-molecule conductance, however, shows significant influence of Mo2 on the properties of the metal string complexes.
A new generation of metal string complexes: Structure, magnetism, spectroscopy, theoretical analysis, and single molecular conductance of an unusual mixed-valence linear [Ni5]8+ complex
Liu, Isiah Po-Chun,Benard, Marc,Hasanov, Hasan,Chen, I.-Wen Peter,Tseng, Wei-Hsiang,Fu, Ming-Dung,Rohmer, Marie-Madeleine,Chen, Chun-Hsien,Lee, Gene-Hsiang,Peng, Shie-Ming
, p. 8667 - 8677 (2007)
Two new linear pentanickel complexes [Ni,(bna)4(Cl) 2][PF6]2 (1) and [Ni5(bna) 4(Cl)2][PF6]4 (2; bna = binaphthyridylamide). were synthesized and structurally characterized. A derivative of 1, [Ni5(bna)4(NCS)2][NCS] 2 (3), was also isolated for the purpose of the conductance experiments carried out in comparison with [Ni5(tpda) 4-(NCS)2] (4; tpda = tripyridyldiamide). The metal framework of complex 2 is a standard [Ni5]10+ core, isoelectronic with that of [Ni5(tpda)4Cl2] (5). Also as in 5. complex 2 has an antiferromagnetic ground state (J = -15.86 cm-1) resulting from a coupling between the terminal nickel atoms, both in high-spin sate (5=1). Complex 1 displays the first characterized linear nickel framework in which the usual sequence of NiII atoms has been reduced by two electrons. Each dinickel unit attached to the naphthyridyl moieties is assumed to undergo a one-electron reduction, whereas the central nickel formally remains NiII. DFT; calculations suggest that the metal framework of the mixed-valence complex 1 should be described as intermediate between a localized picture corresponding to NiII- NiI-NiII-NiI-NiII and a fully delocalized model represented as (Ni2)3+-Ni II-(Ni2)3+. Assuming the latter model, the ground state of 1 results from an antiferromagnetic coupling (J = -34.03 cm -1) between the two (Ni2)3+ fragments, considered each as a single magnetic centre (5 = 3/2). An intervalence charge-transfer band is observed in the NIR spectrum of 1 at 1186nm, suggesting, in accordance with DFT calculations, that 1 should be assigned to Robin-Day class II of mixed-valent complexes. Scanning tunnelling microscopy (STM) methodology was used to assess the conductance of single molecules of 3 and 4. Compound 3 was found ≈ 40% more conductive than 4, a result that could be assigned to the electron mobility induced by mixed-valency in the naphthyridyl fragments.
Conformational change in the association of a heterocyclic urea derivative forming two intramolecular hydrogen bonds in polar solvent
Kwiatkowski, Adam,Grela, Izabela,O?mia?owski, Borys
, p. 1073 - 1081 (2017/02/10)
The association of a model, heterocyclic compound capable of forming two intramolecular hydrogen bonds was studied with the use of various anionic and neutral species in highly polar solvents, but also, for some of them, in chloroform. The hydrogen bonding of anions was tuned through the substituents present in their structures. This approach was used in distinguishing which part of the bisurea heterocyclic derivative is preferred during complex formation. Neutral counterparts capable of forming three or five hydrogen bonds were also used. Moreover, triple association was probed, suggesting the formation of a complex only in chloroform. DFT computations were helpful in the interpretation of the experimental data related to complicated equilibria. These are based on the energy of rotation about single bonds, energy of interaction and QTAIM-based energies of hydrogen bonds.
