The synthesis and the photophysics of three dinuclear copper(I) complexes containing bis(bidentate)phosphine ligands are described. The steric constraint imposed by tetrakis(di(2-methoxyphenyl)phosphanyl)cyclobutane) (o-MeO-dppcb) in combination with 2,9-dimethyl-1,10-phenanthroline in one of the complexes leads to interesting photophysical properties. The compound shows an intense emission at room temperature in deoxygenated acetonitrile solution (Φ = 49%) and a long excited-state lifetime (13.8 μs). Interestingly, at low temperature, 77 K, the emission maximum shifts to lower energy, and the excited-state lifetime increases. This observation leads to the conclusion that a mixing between the excited triplet and singlet states is possible and that the degree of mixing and population of state strongly depends on temperature, as the energy difference is quite small. The electroluminescent properties of this compound were therefore tested in light-emitting electrochemical cells (LEECs), proving that the bright emission can also be obtained by electrically driven population of the singlet state.

The trigonal indium borate InBO(OH) was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 13 GPa and 1150 °C. The crystal structure could be determined by single-crystal X-ray diffraction data collected at room temperature. InBO(OH) crystallizes in the trigonal space group R3̅ (Z = 3) with the lattice parameters a = 1802.49(6) pm, c = 1340.46(5) pm, and V = 3.7716(3) nm. The structure of InBO(OH) contains alternating B-O T2 supertetrahedra units. The presence of hydroxyl groups was confirmed with vibrational spectroscopic methods such as Raman and IR. Besides HInBO, InBO(OH) is now the second known compound in the system In-B-O-H.

No abstract

Most of the systems for photochemical hydrogen production are not stable and suffer from decomposition. With bis(bidentate) tetraphosphane ligands the stability increases enormously, up to more than 1000 h. This stability was achieved with a system containing osmium(ii) as a light harvesting antenna and palladium(ii) as a water reduction catalyst connected with a bis(bidentate) phosphane ligand in one molecule with the chemical formula [Os(bpy)(dppcb)Pd(dppm)](PF). With the help of electrochemical measurements as well as photophysical data and its single crystal X-ray structure, the electron transfer between the two active metal centres (light harvesting antenna, water reduction catalyst) was analysed. The distance between the two active metal centres was determined to be 7.396(1) Å. In a noble metal free combination of a copper based photosensitiser and a cobalt diimine-dioxime complex as water reduction catalyst a further stabilisation effect by the phosphane ligands is observed. With the help of triethylamine as a sacrificial donor in the presence of different monophosphane ligands it was possible to produce hydrogen with a turnover number of 1176. This completely novel combination is also able to produce hydrogen in a wide pH-range from pH = 7.0 to 12.5 with the maximum production at pH = 11.0. The influence of monophosphane ligands with different Tolman cone angles was investigated. Monophosphane ligands with a large Tolman cone angle (>160°) could not stabilise the intermediate of the cobalt based water reduction catalyst and so the turnover number is lower than for systems with an addition of monophosphane ligands with a Tolman cone angle smaller than 160°. The role of the monophosphane ligand during sunlight-induced hydrogen production was analysed and these results were confirmed with DFT calculations. Furthermore the crystal structures of two important Co(i) intermediates, which are the catalytic active species during the catalytic pathway, were obtained. The exchange of PPh with other tertiary phosphane ligands can have a major impact on the activity, depending on the coordination properties. By an exchange of monophosphane ligands with functionalised phosphane ligands (hybrid ligands) the hydrogen production was raised 2.17 times.

The bis(bidentate) phosphane cis,trans,cis-1,2,3,4-tetrakis-(diphenylphosphanyl)cyclobutane (dppcb) has been used for the synthesis of supramolecular complexes, so-called dyads and triads. Depending on the monometallic precursor compound [Ru(bpy) 2 (dppcb)](PF 6 ) 2 or [Ru(bpy) 2 (cis-dppcbO 2 )]-(PF 6 ) 2 [bpy = 2,2Ј-bipyridine, cis-dppcbO 2 = cis,trans,cis-1,2bis(diphenylphosphanoyl)-3,4-bis(diphenylphosphanyl)cyclobutane], [Ru(bpy) 2 (dppcb)NiBr 2 ](PF 6 ) 2 (1) or ΔΛ/ΛΔ-[{Ru(bpy) 2 (cis-dppcbO 2 )} 2 NiBr](PF 6 ) 5 (2) is exclusively formed in good yield by reaction with [NiBr 2 (DME)] (DME = dimethoxyethane). The versatile coordination behaviour of dppcb compared with that of cis-dppcbO 2 is confirmed by cis,trans,cis-2,3-bis(diphenylphosphanoyl)-1,4-bis(diphenylphosphanyl)cyclobutane (2,3-trans-dppcbO 2 , 4). Although two dppcb ligands coordinated simultaneously to a Pd II centre cannot produce a square-planar PdP 4 core, the reaction of two equivalents of 4 with [Pd(CH 3 CN) 4 ](BF 4 ) 2 exclusively leads to meso-(MMMP/MPPP)-[Pd(2,3-trans-dppcbO 2 -[a] 5122 trans-dppcbO 2 , 4) [11] in isolated form with palladium(II) was also investigated (Scheme 2). Usually, it is not possible to combine two dppcb ligands with one palladium(II) centre to generate a square-planar PdP 4 core. [12] However, two equivalents of 4 and one equivalent of [Pd(CH 3 CN) 4 ]-(BF 4 ) 2 exclusively produce meso-(MMMP/MPPP)-[Pd(2,3trans-dppcbO 2 -P,PЈ) 2 ](BF 4 ) 2 (3), which has this square-Eur. J. Inorg. Chem. 2013, 5121-5132