Preparation of carboxylate derivatives of terpyridine via the furan pathway.

This protocol describes a practical procedure for the preparation of terpyridine carboxy derivatives, which have numerous applications, including being photoactive components of functional materials, and which can be used in medicinal chemistry or in catalysis. This protocol relies on the permanganate-mediated oxidation of a furan ring on the polypyridine system. The procedure involves three stages. First, a furan-functionalized terpyridine is synthesized from furfuraldehyde and a 2-acetylpyridine derivative. Second, the furan ring is oxidized thus providing a carboxylic acid. Finally, esters are prepared by reaction of the acids in refluxing alcohols. The procedure is simple, uses a reagent available from renewable resources (furfural) and avoids the use of noxious reagents or solvents, thus making it more environmentally friendly when compared with previously described methods. The whole protocol can be conducted in ∼10 d, including isolation and drying of intermediates and products.

Probing excited state electronic communications across diethynyl-[2.2]paracyclophane-containing conjugated organometallic polymers.

The triplet k(ET) for three organometallic polymers built upon the diethynyl[2.2]paracyclophane was studied to show good excited state electronic communication across the materials.

2-(2,2-Dibromo-ethen-yl)thio-phene.

The title compound, C(6)H(4)Br(2)S, represents a versatile building block for the preparation of π-conjugated redox-active thienyl oligomers and metal-mediated cross-coupling reactions. This is due to the presence of an electrochemically active thienyl heterocycle and a reactive dibromo-vinyl substituent, which easily undergoes dehydro-bromination in the presence of n-butyl-lithium to afford 2-ethynyl-thio-phene. In the molecule, the alkenyl unit and the thio-phene ring are almost coplanar with an angle of 3.5 (2)° between the normals of the best planes of the thio-phene ring and the vinyl moiety.

Properties of the [M(dppm)2M']2+ building blocks (M, M' = Pd or Pt): site selectivity, emission features, and frontier orbital analysis.

The homodinuclear [ClM(mu-dppm)(2)MCl] complexes 1 (M = Pd) and 2 (M = Pt) react with RNC ligands (R = Ph, xylyl, p-tolyl, p-C(6)H(4)iPr) to provide the A-frame [ClPd(mu-dppm)(2)(mu-C=N-R)PdCl] (R = Ph (5a), xylyl (5b)), [ClPt(mu-dppm)(2)(mu-C=N-R)PtCl] (R = p-tolyl (4a); p-C(6)H(4)iPr (4b)), and the d(9)-d(9) M(2)-bonded [ClPt(mu-dppm)(2)Pt(CN-R)]Cl (R = xylyl (3a); p-C(6)H(4)iPr (3b)) complexes. The heterodinuclear [XPd(mu-dppm)(2)PtX] complexes 6a (X = Cl) and 6b (X = I) react with RNC (R = o-anisyl) to form the A-frame [XPd(mu-dppm)(2)(mu-C=N-R)PtX] (X = Cl (9); I (10a)) and M(2)-bonded [ClPt(mu-dppm)(2)Pt(CN-R)]Cl (10b) complexes. The dangling ligand-containing complex [ClPd(mu-dppm)(2)Pt(eta(1)-dppm=O)](BF(4)) (7) reacts with xylyl-NC stoichiometrically to produce the dicationic salt [(xylyl-NC)Pd(mu-dppm)(2)Pt(eta(1)-dppm=O)](BF(4))(2) (8). Parameters ruling the coordination site terminal versus bridging are discussed. The precursor 10a reacts with RNC (R = o-anisyl, tBu) to form the heterobimetallic bis(isonitrile) [IPd(mu-dppm)(2)(mu-C=N-o-anisyl)Pt(CN-R)]I complexes 11b and 12, respectively, demonstrating the site selectivity of the second CNR ligand coordination, Pd versus Pt. The X-ray structures of 11b and 12 were obtained. Complex 12 is the first example of an A-frame system of the Ni-triad bearing two different isocyanide ligands. Several d(9)-d(9) terminal and d(8)-d(8) A-frame homo- and heterodinuclear complexes in 2-MeTHF at 77 K were studied by UV-vis and luminescence spectroscopy. Assignments for the lowest energy absorption and emission bands are made on the basis of density functional theory and time-dependent density functional theory computations.

(2,2-Dichloro-vinyl)ferrocene.

The title compound, [Fe(C(5)H(5))(C(7)H(5)Cl(2))], represents a versatile building block for the preparation of π-conjugated redox-active compounds or polymetallic organometallic systems due to the presence of the electrochemically active ferrocenyl unit. It is therefore a potential starting material for the preperation of the corresponding alkyne. In the crystal, the alkenyl unit and the cyclo-penta-dienide ring are almost parallel, with an angle between the best planes of only 10.6 (4)°.

4,12-Bis(2,2-dibromo-vinyl)[2.2]paracyclo-phane.

In the title compound, C(20)H(16)Br(4), both vinylic substituents were introduced by a Corey-Fuchs reaction using 4,12-diform-yl[2.2]paracyclo-phane as starting material. The title compound may be used as a valuable precursor for the synthesis of diethyn-yl[2.2]paracyclo-phane. The title mol-ecule is centrosymmetric with a crystallographic center of inversion between the centers of the two phenyl rings. A strong tilting is observed with an inter-planar angle between the best aromatic plane and the vinyl plane of 49.4 (5)°. No significant inter-molecular inter-actions are found in the crystal.

Probing the electronic communication of the isocyanide bridge through the luminescence properties of the d9-d9 [ClPt(mu-dppm)2Pt(C triple bond N-PCP)]+ and A-Frame [ClPd(mu-dppm)2(mu-C=N-PCP)PdCl] complexes.

The homodinuclear d9-d9 ClM(mu-dppm)2MCl2 complexes, 1 (M ) Pt) and 2 (M ) Pd) react with the conjugated and luminescent PCP-NC ligand (3, PCP ) [2.2]paracyclophane) to provide the corresponding d9-d9 terminal[ClPt(mu-dppm)2Pt(CNsPCP)]Cl (4) and d8-d8 A-frame [ClPd(mu-dppm)2(mu-CdNsPCP)PdCl] (5) isocyanide complexes, respectively. These two bimetallic complexes were characterized by IR, 1H, and 31P{1H} NMR and bychemical analysis. IR data (nu(CN) bridging vs terminal) reveal a terminal isocyanide bonding mode for 4 (2147cm(-1)) and an A-frame structure for 5 (1616 cm(-1)). The optical and emission properties of the free isocyanide 3as well as those of the homodinuclear complexes 4 and 5 were studied by UV-visible and luminescence spectroscopy and by photophysical measurements. The unexpected presence of simultaneous intraligand pipi* fluorescence and phosphorescence attributable to the organic PCP-NC ligand, as well as luminescence from the inorganic M2-bonded Pt2(mu-dppm)2 center arising from a lower energy excited LMCT state (ligand-to-metal-charge-transfer) for4 at 77 K, indicates a weak conjugation between the two chromophores and an absence of efficient singlet andtriplet energy transfers. For 5, only the fluorescence and phosphorescence bands of the PCP-NC ligand are observed [since the A-frame XPd(mu-dppm)2(mu-L)PdX (L ) isocyanide, X ) halide) is not luminescent], stressing that the NtC bridge exhibits modest electronic communication properties.