Effects of fluorine on the structures and energetics of the propynyl and propargyl radicals and their anions

[reaction: see text] The adiabatic electron affinity (EA(ad)) of the CH(3)-C[triple bond]C(*) radical [experiment = 2.718 +/- 0.008 eV] and the gas-phase basicity of the CH(3)-C[triple bond]C:(-) anion [experiment = 373.4 +/- 2 kcal/mol] have been compared with those of their fluorine derivatives. The latter are studied using theoretical methods. It is found that there are large effects on the electron affinities and gas-phase basicities as the H atoms of the alpha-CH(3) group in the propynyl system are substituted by F atoms. The predicted electron affinities are 3.31 eV (FCH(2)-C[triple bond]C(*)), 3.86 eV (F(2)CH-C[triple bond]C(*)), and 4.24 eV (F(3)C-C[triple bond]C(*)), and the predicted gas-phase basicities of the fluorocarbanion derivatives are 366.4 kcal/mol (FCH(2)-C[triple bond]C:(-)), 356.6 kcal/mol (F(2)CH-C[triple bond]C:(-)), and 349.8 kcal/mol (F(3)C-C[triple bond]C:(-)). It is concluded that the electron affinities of fluoropropynyl radicals increase and the gas-phase basicities decrease as F atoms sequentially replace H atoms of the alpha-CH(3) in the propynyl system. The propargyl radicals, lower in energy than the isomeric propynyl radicals, are also examined and their electron affinities are predicted to be 0.98 eV ((*)CH(2)-C[triple bond]CH), 1.18 eV ((*)CFH-C[triple bond]CH), 1.32 eV ((*)CF(2)-C[triple bond] CH), 1.71 eV ((*)CH(2)-C[triple bond]CF), 2.05 eV ((*)CFH-C[triple bond]CF), and 2.23 eV ((*)CF(2)-C[triple bond]CF).     

Asymmetry in platinum acetylide complexes: confinement of the triplet exciton to the lowest energy ligand

To determine structure-optical property relationships in asymmetric platinum acetylide complexes, we synthesized the compounds trans-Pt(PBu3)2(C[triple bond]CC6H5)(C[triple bond]C-C6H4-C[triple bond]CC6H5) (PE1-2), trans-Pt(PBu3)2(C[triple bond]CC6H5)(C[triple bond]C-C6H4-C[triple bond]C-C6H4-C[triple bond]CC6H5) (PE1-3) and trans-Pt(PBu3)2(C[triple bond]C-C6H4-C[triple bond]CC6H5)(C[triple bond]C-C6H4-C[triple bond]C-C6H4-C[triple bond]CC6H5) (PE2-3) that have different ligands on either side of the platinum and compared their spectroscopic properties to the symmetrical compounds PE1, PE2 and PE3. We measured ground state absorption, fluorescence, phosphorescence and triplet state absorption spectra and performed density functional theory (DFT) calculations of frontier orbitals, lowest lying singlet states, triplet state geometries and energies. The absorption and emission spectra give evidence the singlet exciton is delocalized across the central platinum atom. The phosphorescence from the asymmetric complexes comes from the largest ligand. Time-dependent (TD) DFT calculations show the S1 state has mostly highest occupied molecular orbital (HOMO) --> lowest unoccupied molecular orbital (LUMO) character, with the LUMO delocalized over the chromophore. In the asymmetric chromophores, the LUMO resides on the larger ligand, suggesting the S1 state has interligand charge transfer character. The triplet state geometries obtained from the DFT calculations show distortion on the lowest energy ligand, whereas the other ligand has the ground state geometry. The calculated trend in the triplet state energies agrees very well with the experimental trend. Calculations of triplet state spin density also show the triplet exciton is confined to one ligand. In the asymmetric complexes the spin density is confined to the largest ligand. The results show Kasha's rule applies to these complexes, where the triplet exciton moves to the lowest energy ligand.     

Aluminacyclopropene: syntheses, characterization, and reactivity toward terminal alkynes

Reactions of LAl with ethyne, mono- and disubstituted alkynes, and diyne to aluminacyclopropene LAl[eta2-C2(R1)(R2)] ((L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3); R1 = R2 = H, (1); R1 = H, R2 = Ph, (2); R1 = R2 = Me, (3); R1 = SiMe3, R2 = C[triple bond]CSiMe3, (4)) are reported. Compounds 1 and 2 were obtained in equimolar quantities of the starting materials at low temperature. The amount of C2H2 was controlled by removing an excess of C2H2 in the range from -78 to -50 degrees C. Compound 4 can be alternatively prepared by the substitution reaction of LAl[eta2-C2(SiMe3)2] with Me3SiC[triple bond]CC[triple bond]CSiMe3 or by the reductive coupling reaction of LAlI2 with potassium in the presence of Me3SiC[triple bond]CC[triple bond]CSiMe3. The reaction of LAl with excess C2H2 and PhC[triple bond]CH (<1:2) afforded the respective alkenylalkynylaluminum compounds LAl(CH=CH2)(C[triple bond]CH) (5) and LAl(CH=CHPh)(C[triple bond]CPh) (6). The reaction of LAl(eta2-C2Ph2) with C2H2 and PhC[triple bond]CH yielded LAl(CPh=CHPh)(C[triple bond]CH) (7) and LAl(CPh=CHPh)(C[triple bond]CPh) (8), respectively. Rationally, the formation of 5 (or 6) may proceed through the corresponding precursor 1 (or 2). The theoretical studies based on DFT calculations show that an interaction between the Al(I) center and the C[triple bond]C unit needs almost no activation energy. Within the AlC2 ring the computational Al-C bond order of ca. 1 suggests an Al-C sigma bond and therefore less pi electron delocalization over the AlC2 ring. The computed Al-eta2-C2 bond dissociation energies (155-82.6 kJ/mol) indicate a remarkable reactivity of aluminacyclopropene species. Finally, the 1H NMR spectroscopy monitored reaction of LAl(eta2-C2Ph2) and PhC[triple bond]CH in toluene-d8 may reveal an acetylenic hydrogen migration process.     

Amidinate-carboxylate complexes of dimolybdenum and ditungsten: M2(O2CR)2((NiPr)2CR')2. Preparations, molecular and electronic structures and reactions.

The compounds M(2)(O(2)CMe)(4) and the lithium amidinates Li[(N(i)Pr)(2)CR] react to give the new compounds trans-M(2)(O(2)CMe)(2)[(N(i)Pr)(2)CR](2) where M = Mo or W and R = Me (M = Mo only), -C[triple bond]C(t)Bu, -C[triple bond]CPh and -C[triple bond]C-Fc where Fc = 1-ferrocenyl. The limitations of this type of reaction are described based on steric considerations together with the preparation and characterization of the compound Mo(2)(micro-O(2)C-9-anthracene)(2)[eta(2)-(N(i)Pr)(2)CMe](2). The electronic structures of the bis-amidinate-bis-carboxylate M(2) complexes are described based on model compounds employing density functional theory and are correlated with the experimental observations of their physicochemical properties and in particular their observed electronic absorption spectra which show intense MLCT absorption bands. Preliminary studies of the reactions of these bis-amidinate-bis-carboxylate complexes in the preparation of 1-D oligomers are also described along with the preparation and molecular structures of the compounds [Li(N(i)Pr)(2)CR.THF](2) where R = 2-thienyl or -C[triple bond]C-Ph. The kinetic lability of these new M(2)-containing compounds toward ligand exchange is also noted.     

Synthesis and characterization of mono- and binuclear platinum complexes containing terminal and bridging diynyldiphenylphosphine ligands

A series of mononuclear platinum complexes containing diynyldiphenylphosphine ligands [cis-Pt(C(6)F(5))(2)(PPh(2)C[triple bond]CC(6)H(4)C[triple bond]CR)L](n)(n= 0, L = tht, R = Ph 2a, Bu(t)2b; L = PPh(2)C[triple bond]CC(6)H(4)C[triple bond]CR, 4a, 4b; n=-1, L = CN(-), 3a, 3b) has been synthesized and the X-ray crystal structures of 4a and 4b have been determined. In order to compare the eta2-bonding capability of the inner and outer alkyne units, the reactivity of towards [cis-Pt(C(6)F(5))(2)(thf)(2)] or [Pt(eta2)-C(2)H(4))(PPh(3))(2)] has been examined. Complexes coordinate the fragment "cis-Pt(C(6)F(5))(2)" using the inner alkynyl fragment and the sulfur of the tht ligand giving rise the binuclear derivatives [(C(6)F(5))(2)Pt(mu-tht)(mu-1kappaP:2eta2-C(alpha),C(beta)-PPh(2)C[triple bond]CC(6)H(4)C[triple bond]CR)Pt(C(6)F(5))(2)](R = Ph 5a, Bu(t)5b). The phenyldiynylphosphine complexes 2a, 3a and 4a react with [Pt(eta2)-C(2)H(4))(PPh(3))(2)] to give the mixed-valence Pt(II)-Pt(0) complexes [((C(6)F(5))(2)LPt(mu-1kappaP:2eta2)-C(5),C(6)-PPh(2)C[triple bond]CC(6)H(4)C[triple bond]CPh))Pt(PPh(3))(2)](n)(L = tht 6a, CN 8a and PPh(2)C[triple bond]CC(6)H(4)C[triple bond]CPh 9a) in which the Pt(0) fragment is eta2-complexed by the outer fragment. Complex 6a isomerizes in solution to a final complex [((C(6)F(5))(2)(tht)Pt(mu-1kappaP:2eta2)-C(alpha),C(beta)-PPh(2)C[triple bond]CC(6)H(4)C[triple bond]CPh))Pt(PPh(3))(2)]7a having the Pt(0) fragment coordinated to the inner alkyne function. In contrast, the tert-butyldiynylphosphine complexes 2b and 3b coordinate the Pt(0) unit through the phosphorus substituted inner acetylenic entity yielding 7b and 8b. By using 4a and 2 equiv. of [Pt(eta2)-C(2)H(4))(PPh(3))(2)] as precursors, the synthesis of the trinuclear complex [cis-((C(6)F(5))(2)Pt(mu-1kappaP:2eta2)-C(5),C(6)-PPh(2)C[triple bond]CC(6)H(4)C[triple bond]CPh)(2))(Pt(PPh(3))(2))(2)]10a, bearing two Pt(0)(PPh(3))(2)eta2)-coordinated to the outer alkyne functions is achieved. The structure of 7a has been confirmed by single-crystal X-ray diffraction.     

Novel luminescent mixed-metal Pt-Tl-alkynyl-based complexes: the role of the alkynyl substituent in metallophilic and eta2(pi...Tl)-bonding interactions

A novel series of [PtTl(2)(C[triple chemical bond]CR)(4)](n) (n = 2, R = 4-CH(3)C(6)H(4) (Tol) 1, 1-naphthyl (Np) 2; n = infinity, R = 4-CF(3)C(6)H(4) (Tol(F)) 3) complexes has been synthesized by neutralization reactions between the previously reported [Pt(C[triple chemical bond]CR)(4)](2-) (R = Tol, Tol(F)) or novel (NBu(4))(2)[Pt(C[triple chemical bond]CNp)(4)] platinum precursors and Tl(I) (TlNO(3) or TlPF(6)). The crystal structures of [Pt(2)Tl(4)(C[triple chemical bond]CTol)(8)]4 acetone, 14 acetone, [Pt(2)Tl(4)(C[triple chemical bond]CNp)(8)]3 acetone1/3 H(2)O, 23 acetone 1/3 H(2)O and [[PtTl(2)(C[triple chemical bond]CTol(F))(4)](acetone)S](infinity) (S = acetone 3 a; dioxane 3 b) have been solved by X-ray diffraction studies. Interestingly, whereas in the tolyl (1) and naphthyl (2) derivatives, the thallium centers exhibit a bonding preference for the electron-rich alkyne entities to yield crystal lattices based on sandwich hexanuclear [Pt(2)Tl(4)(C[triple chemical bond]CR)(8)] clusters (with additional Tlacetone (1) or Tlnaphthyl (2) secondary interactions), in the C(6)H(4)CF(3) (Tol(F)) derivatives 3 a and 3 b the basic Pt(II) center forms two unsupported Pt-Tl bonds. As a consequence 3 a and 3 b form an extended columnar structure based on trimetallic slipped PtTl(2)(C[triple chemical bond]CTol(F))(4) units that are connected through secondary Tl(eta(2)-acetylenic) interactions. The luminescent properties of these complexes, which in solution (blue; CH(2)Cl(2) 1,2; acetone 3) are very different to those in solid state (orange), have been studied. Curiously, solid-state emission from 1 is dependent on the presence of acetone (green) and its crystallinity. On the other hand, while a powder sample of 3 is pale yellow and displays blue (457 nm) and orange (611 nm) emissions, the corresponding pellets (KBr, solid) of 3, or the fine powder obtained by grinding, are orange and only exhibit a very intense orange emission (590 nm).     

Mixed-transition-metal acetylides: synthesis and characterization of complexes with up to six different transition metals connected by carbon-rich bridging units

The synthesis and reaction chemistry of heteromultimetallic transition-metal complexes by linking diverse metal-complex building blocks with multifunctional carbon-rich alkynyl-, benzene-, and bipyridyl-based bridging units is discussed. In context with this background, the preparation of [1-{(eta(2)-dppf)(eta(5)-C(5)H(5))RuC[triple bond]C}-3-{(tBu(2)bpy)(CO)(3)ReC[triple bond]C}-5-(PPh(2))C(6)H(3)] (10) (dppf = 1,1'-bis(diphenylphosphino)ferrocene; tBu(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridyl; Ph = phenyl) is described; this complex can react further, leading to the successful synthesis of heterometallic complexes of higher nuclearity. Heterotetrametallic transition-metal compounds were formed when 10 was reacted with [{(eta(5)-C(5)Me(5))RhCl(2)}(2)] (18), [(Et(2)S)(2)PtCl(2)] (20) or [(tht)AuC[triple bond]C-bpy] (24) (Me = methyl; Et = ethyl; tht = tetrahydrothiophene; bpy = 2,2'-bipyridyl-5-yl). Complexes [1-{(eta(2)-dppf)(eta(5)-C(5)H(5))RuC[triple bond]C}-3-{(tBu(2)bpy)(CO)(3)ReC[triple bond]C}-5-{PPh(2)RhCl(2)(eta(5)-C(5)Me(5))}C(6)H(3)] (19), [{1-[(eta(2)-dppf)(eta(5)-C(5)H(5))RuC[triple bond]C]-3-[(tBu(2)bpy)(CO)(3)ReC[triple bond]C]-5-(PPh(2))C(6)H(3)}(2)PtCl(2)] (21), and [1-{(eta(2)-dppf)(eta(5)-C(5)H(5))RuC[triple bond]C}-3-{(tBu(2)bpy)(CO)(3)ReC[triple bond]C}-5-{PPh(2)AuC[triple bond]C-bpy}C(6)H(3)] (25) were thereby obtained in good yield. After a prolonged time in solution, complex 25 undergoes a transmetallation reaction to produce [(tBu(2)bpy)(CO)(3)ReC[triple bond]C-bpy] (26). Moreover, the bipyridyl building block in 25 allowed the synthesis of Fe-Ru-Re-Au-Mo- (28) and Fe-Ru-Re-Au-Cu-Ti-based (30) assemblies on addition of [(nbd)Mo(CO)(4)] (27), (nbd = 1,5-norbornadiene), or [{[Ti](mu-sigma,pi-C[triple bond]CSiMe(3))(2)}Cu(N[triple bond]CMe)][PF(6)] (29) ([Ti] = (eta(5)-C(5)H(4)SiMe(3))(2)Ti) to 25. The identities of 5, 6, 8, 10-12, 14-16, 19, 21, 25, 26, 28, and 30 have been confirmed by elemental analysis and IR, (1)H, (13)C{(1)H}, and (31)P{(1)H} NMR spectroscopy. From selected samples ESI-TOF mass spectra were measured. The solid-state structures of 8, 12, 19 and 26 were additionally solved by single-crystal X-ray structure analysis, confirming the structural assignment made from spectroscopy.     

Synthesis and luminescence behaviour of novel heterodecanuclear silver(I)-rhenium(I) alkynyl complexes. X-ray crystal structures of [Ag6(mu-dppm)4[mu3-C[triple bond]CC[triple bond]C-Re(Me2bpy)(CO)3]4](PF6)2 and [Ag6(mu-dppm)4[mu3-C[triple bond]CC[triple bond]C-Re(Br2phen)(CO)3]4](PF6)2

A novel series of luminescent heterodecanuclear mixed-metal alkynyl complexes, [Ag6(mu-dppm)4[mu3-C[triple bond]CC[triple bond]C-Re(N--N)(CO)3]4](PF6)2, (N--N = tBu2bpy, Me2bpy, phen, Br2phen), have been successfully synthesized; the X-ray crystal structures of [Ag6(mu-dppm)4[mu3-C[triple bond]CC[triple bond]C-Re(Me2bpy)(CO)3]4](PF6)2 and [Ag6(mu-dppm)4[mu3-C[triple bond]CC[triple bond]C-Re(Br2phen)(CO)3]4](PF6)2 have also been determined.     

New iridacyclohexadienes and iridabenzenes by [2+2+1] cyclotrimerization of alkynes and facile interconversion between iridacyclohexadienes and iridabenzenes

Iridabenzenes [Ir[=CHCH=CHCH=C(CH2R)](CH3CN)2(PPh3)2]2+ (R=Ph 4 a, R=p-C6H4CH3 4 b) are obtained from the reactions of H+ with iridacyclohexadienes [Ir[-CH=CHCH=CHC(=CH-p-C6H4R')](CO)(PPh3)2]+ (R'=H 3 a, R'=CH3 3 b), which are prepared from [2+2+1] cyclotrimerization of alkynes in the reactions of [Ir(CH3CN)(CO)(PPh3)2]+ with HC[triple chemical bond]CH and HC[triple chemical bond]CR. Iridabenzenes 4 react with CO and CH3CN in the presence of NEt3 to give iridacyclohexadienes [Ir[-CH=CHCH=CHC(=CHR)](CO)2(PPh3)2]+ (6) and [Ir[-CH=CHCH=CHC(=CHR)](CH3CN)2(PPh3)2]+ (7), respectively. Iridacyclohexadienes 6 and 7 also convert to iridabenzenes 4 by the reactions with H+ in the presence of CH3CN. Alkynyl iridacyclohexadienes [Ir[-CH=CHCH=CHC(=CH-p-C6H4R')](-C[triple chemical bond]CH)(PPh3)2] (8) undergo a cleavage of C[triple chemical bond]C bond by H+/H2O to produce [Ir[-CH=CHCH=CHC(=CH-p-C6H4R')](-CH3)(CO)(PPh3)2] (10) via facile inter-conversion between iridacyclohexadienes and iridabenzenes.     

High coordination chemically bound compounds of noble gases with hydrocarbons: Ng(CCH)4 and Ng(CCH)6, (Ng=Xe or Kr)

Ab initio calculations predict the existence of the compounds Ng(-C[triple bond]CH)4 and Ng(-C[triple bond]CH)6, where Ng=Xe or Kr. Presently known organic noble gas compounds have a coordination number of two at most. The Ng(-C[triple bond]CH)(4) molecules have D(4h) symmetry, and Ng(-C[triple bond]CH)(6) molecules have O(h) symmetry. The bonding in all these compounds is partly ionic and partly covalent, with significant contributions from both types of bonding. The relatively high vibrational frequencies and the substantial Ng-(C[triple bond]CH) binding energy in these species indicate that these compounds should be fairly stable, at least in cryogenic conditions. These compounds could be a very interesting addition to the range of known organic noble gas compounds. Suggestions are made on possible approaches to their preparation.     

The d4/d3 redox pairs [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']z (z=0 and 1): structural consequences of electron transfer and implications for the inverse halide order

The d4 halide complexes [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp'] {X=F, Cl, Br or I; R=Me or Ph; M=Mo or W; Tp'=hydrotris(3,5-dimethylpyrazolyl)borate} undergo one-electron oxidation to the d3 monocations [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']+, isolable for M=W, R=Me. X-Ray structural studies on the redox pairs [WX(CO)(eta-MeC[triple bond, length as m-dash]CMe)Tp']z (X=Cl and Br, z=0 and 1), the ESR spectra of the cations [WX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']+ (X=F, Cl, Br or I; R=Me or Ph), and DFT calculations on [WX(CO)(eta-MeC[triple bond, length as m-dash]CMe)Tp']z (X=F, Cl, Br and I; z=0 and 1) are consistent with electron removal from a HOMO (of the d4 complexes) which is pi-antibonding with respect to the W-X bond, pi-bonding with respect to the W-C(O) bond, and delta-bonding with respect to the W-Calkyne bonds. The dependence of both oxidation potential and nu(CO) for [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp'] shows an inverse halide order which is consistent with an ionic component to the M-X bond; the small size of fluorine and its closeness to the metal centre leads to the highest energy HOMO and the lowest oxidation potential. In the cations [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']+ electronegativity effects become more important, leading to a conventional order for Cl, Br and I. However, high M-F pi-donation is still facilitated by the short M-F distance.     

Diazaborolyl-boryl push-pull systems with ethynylene-arylene bridges as 'turn-on' fluoride sensors

Two linear π-conjugated systems with 1,3-diethyl-1,3,2-benzodiazaborolyl [C(6)H(4)(NEt)(2)B-] as a donor group and dimesitylboryl (-BMes(2)) as acceptor were synthesised with -ethynylene-phenylene- (-C[triple bond, length as m-dash]C-1,4-C(6)H(4)-, 3) and -ethynylene-thiophene- (-C[triple bond, length as m-dash]C-2,5-C(4)H(2)S-12) bridges between the boron atoms. An assembly (20) consisting of two diazaborolyl-ethynylene-phenylene-boryl units, [C(6)H(4)(NCy)(N')B-C[triple bond, length as m-dash]C-1,4-C(6)H(4)-BMes(2)] joined via a 1,4-phenylene unit at the nitrogen atoms (N') of the diazaborolyl units was also synthesised. The three push-pull systems, 3, 12 and 20, form salts on fluoride addition with the BMes(2) groups converted into (BMes(2)F)(-) anions. The molecular structures of 3, 12 and (NBu(4))(12·F) were elucidated by X-ray diffraction analyses. The borylated systems 3, 12 and 20 show intense blue luminescence in cyclohexane with quantum yields (Φ(fl)) of 0.99, 0.44 and 0.94, respectively, but weak blue-green luminescence in tetrahydrofuran (Φ(fl) = 0.02-0.05). The charge transfer nature of these transitions is supported by TD-DFT computations with the CAM-B3LYP functional. Addition of tetrabutylammonium fluoride to tetrahydrofuran solutions of 3 and 20 resulted in strong violet-blue luminescence with emission intensities up to 46 times more than the emission intensities observed prior to fluoride addition. Compounds 3 and 20 are demonstrated here as remarkable 'turn-on' fluoride sensors in tetrahydrofuran solutions.     

Synthesis and properties of alkynethiolate gold(I) complexes

A series of alkynethiolate gold(I) derivatives have been synthesised by the cleavage of 4-monosubstituted 1,2,3-thiadiazoles in the presence of strong bases. The syntheses of the 1.2,3-thiadiazoles with p-cyanophenyl, p-tolyl, 2-thienyl, 3-thienyl and 9,9-dimethylfluoren-2-yl fragments are also described. All the complexes have been characterised by spectroscopic techniques and the complexes [Au(p-CH3-C6H4-C[triple bond]C-S)PPh3], [Au(3-C4H3S-C[triple bond]C-S)PPh3] and PPN[Au(p-CH3-C6H4-C[triple bond]C-S)(C6F5)] by X-ray analysis. The electrochemically polymerizable mononuclear bis(alkynethiolate) gold(I) complex PPN[Au(3-C4H3S-C[triple bond]C-S)2] is also described, including its electropolymerization and electrochemical properties.     

Probing ruthenium-acetylide bonding interactions: synthesis, electrochemistry, and spectroscopic studies of acetylide-ruthenium complexes supported by tetradentate macrocyclic amine and diphosphine ligands

The synthesis and spectroscopic properties of trans-[RuL4(C[triple bond]CAr)2] (L4 = two 1,2-bis(dimethylphosphino)ethane, (dmpe)2; 1,5,9,13-tetramethyl-1,5,9,13-tetraazacyclohexadecane, 16-TMC; 1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane, N2O2) are described. Investigations into the effects of varying the [RuL4] core, acetylide ligands, and acetylide chain length for the [(-)C[triple bond]C(C6H4C[triple bond]C)(n-1)Ph] and [(-)C[triple bond]C(C6H4)(n-1)Ph] (n = 1-3) series upon the electronic and electrochemical characteristics of trans-[RuL4(C[triple bond]CAr)2](0/+) are presented. DFT and TD-DFT calculations have been performed on trans-[Ru(L')4(C[triple bond]CAr)2](0/+) (L' = PH3 and NH3) to examine the metal-acetylide pi-interaction and the nature of the associated electronic transition(s). It was observed that (1) the relationship between the transition energy and 1/n for trans-[Ru(dmpe)2{C[triple bond]C(C6H4C[triple bond]C)(n-1)Ph}2] (n = 1-3) is linear, and (2) the sum of the d(pi)(Ru(II)) --> pi*(C[triple bond]CAr) MLCT energy for trans-[Ru(16-TMC or N2O2)(C[triple bond]CAr)2] and the pi(C[triple bond]CAr) --> d(pi)(Ru(III)) LMCT energy for trans-[Ru(16-TMC or N2O2)(C[triple bond]CAr)2]+ corresponds to the intraligand pi pi* absorption energy for trans-[Ru(16-TMC or N2O2)(C[triple bond]CAr)2]. The crystal structure of trans-[Ru(dmpe)2{C[triple bond]C(C6H4C[triple bond]C)2Ph}2] shows that the two edges of the molecule are separated by 41.7 A. The electrochemical and spectroscopic properties of these complexes can be systematically tuned by modifying L4 and Ar to give E(1/2) values for oxidation of trans-[RuL4(C[triple bond]CAr)2] that span over 870 mV and lambda(max) values of trans-[RuL4(C[triple bond]CAr)2] that range from 19,230 to 31,750 cm(-1). The overall experimental findings suggest that the pi-back-bonding interaction in trans-[RuL4(C[triple bond]CAr)2] is weak and the [RuL4] moiety in these molecules may be considered to be playing a "dopant" role in a linear rigid pi-conjugated rod.     

Radical ion states of platinum acetylide oligomers

The ion radicals of two series of platinum acetylide oligomers have been subjected to study by electrochemical and pulse radiolysis/transient absorption methods. One series of oligomers, Ptn, has the general structure Ph-C[triple bond]C-[Pt(PBu3)2-C[triple bond]C-(1,4-Ph)-C[triple bond]C-]n-Pt(PBu3)2-C[triple bond]C-Ph (where x=0-4, Ph=phenyl and 1,4-Ph=1,4-phenylene). The second series of oligomers, Pt4Tn, contain a thiophene oligomer core, -C[triple bond]C-(2,5-Th)n-C[triple bond]C- (where n=1-3 and 2,5-Th=2,5-thienylene), capped on both ends with -Pt(PBu3)2-C[triple bond]C-(1,4-Ph)-C[triple bond]C-Pt(PBu3)2-C[triple bond]C-Ph segments. Electrochemical studies reveal that all of the oligomers feature reversible or quasi-reversible one-electron oxidation at potentials less than 1 V versus SCE. These oxidations are assigned to the formation of radical cations on the platinum acetylide chains. For the longer oligomers multiple, reversible one-electron waves are observed at potentials less than 1 V, indicating that multiple positive polarons can be produced on the oligomers. Pulse-radiolysis/transient absorption spectroscopy has been used to study the spectra and dynamics of the cation and anion radical states of the oligomers in dichloroethane and tetrahydrofuran solutions, respectively. All of the ion radicals exhibit two allowed absorption bands: one in the visible region and the second in the near-infrared region. The ion radical spectra shift with oligomer length, suggesting that the polarons are delocalized to some extent on the platinum acetylide chains. Analysis of the electrochemical and pulse radiolysis data combined with the density functional theory calculations on model ion radicals provides insight into the electronic structure of the positive and negative ion radical states of the oligomers. A key conclusion of the work is that the polaron states are concentrated on relatively short oligomer segments.     

C-C coupling reactions in the coordination sphere of rhodium(I) and rhodium(III): New routes for the di- and trimerization of terminal alkynes

The alkynyl(vinylidene)rhodium(I) complexes trans-[Rh(C[triple bond, length as m-dash]CR)(=C=CHR)(PiPr3)2] 2, 5, 6 react with CO by migratory insertion to give stereoselectively the butenynyl compounds trans-[Rh{eta1-(Z)-C(=CHR)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-7-9, of which (Z)-7 (R=Ph) and (Z)-8 (R=tBu) rearrange upon heating or UV irradiation to the (E) isomers. Similarly, trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CPh}(CO)(PiPr3)2] 12 and trans-[Rh{eta1-(Z)-C(=CHCO2Me)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-15, (Z)-16 have been prepared. At room temperature, the corresponding "non-substituted" derivative trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CH}(CO)(PiPr3)2] 18 is in equilibrium with the butatrienyl isomer trans-[Rh(eta1-CH=]C=C=CH2)(CO)(PiPr3)2] 19 that rearranges photochemically to the alkynyl complex trans-[Rh(C[triple bond, length as m-dash]CCH=CH2)(CO)(PiPr3)2] 20. Reactions of (Z)-7, (E)-7, (Z)-8 and (E)-8 with carboxylic acids R'CO2H (R'=CH3, CF3) yield either the butenyne (Z)- and/or (E)-RC[triple bond, length as m-dash]CCH=CHR or a mixture of the butenyne and the isomeric butatriene, the ratio of which depends on both R and R'. Treatment of 2 (R=Ph) with HCl at -40 degrees C affords five-coordinate [RhCl(C[triple bond, length as m-dash]CPh){(Z)-CH=CHPh}(PiPr3)2] 23, which at room temperature reacts by C-C coupling to give trans-[RhCl{eta2-(Z)-PhC[triple bond, length as m-dash]CCH=CHPh}(PiPr3)2](Z)-21. The related compound trans-[RhCl(eta2-HC[triple bond, length as m-dash]CCH=CH2)(PiPr3)2] 27, prepared from trans-[Rh(C[triple bond, length as m-dash]CH)(=C=CH2)(PiPr3)2] 17 and HCl, rearranges to the vinylvinylidene isomer trans-[RhCl(=C=CHCH=CH2)(PiPr3)2] 28. While stepwise reaction of 2with CF3CO2H yields, via alkynyl(vinyl)rhodium(III) intermediates (Z)-29 and (E)-29, the alkyne complexes trans-[Rh(kappa1-O2CCF3)(eta2-PhC[triple bond, length as m-dash]CCH=CHPh)(PiPr3)2](Z)-30 and (E)-30, from 2 and CH3CO2H the acetato derivative [Rh(kappa2-O2CCH3)(PiPr3)2] 33 and (Z)-PhC[triple bond, length as m-dash]CCH=]CHPh are obtained. From 6 (R=CO2Me) and HCl or HC[triple bond, length as m-dash]CCO2Me the chelate complexes [RhX(C[triple bond, length as m-dash]CCO2Me){kappa2(C,O)-CH=CHC(OMe)=O}(PiPr3)2] 34 (X=Cl) and 35 (X=C[triple bond, length as m-dash]CCO2Me) have been prepared. In contrast to the reactions of [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE)(CH=CHE)(PiPr3)2] 37(E=CO2Me) with chloride sources which give, via intramolecular C-C coupling, four-coordinate trans-[RhCl{eta2-(E)-EC[triple bond, length as m-dash]CCH=CHE}(PiPr3)2](E)-36, treatment of 37with HC[triple bond, length as m-dash]CE affords, via insertion of the alkyne into the rhodium-vinyl bond, six-coordinate [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE){eta1-(E,E)-C(=CHE)CH=CHE}(PiPr3)2] 38. The latter reacts with MgCl2 to yield trans-[RhCl{eta2-(E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE}(PiPr3)2] 39, which, in the presence of CO, generates the substituted hexadienyne (E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE 40.     

Molecular QCA cells. 1. Structure and functionalization of an unsymmetrical dinuclear mixed-valence complex for surface binding

Utilization of binary information encoded in the charge configuration of quantum-dot cells (the quantum-dot cellular automata, QCA, paradigm) requires molecule-sized dots for room temperature operation. Molecular QCA cells are mixed-valence complexes, and the evaluation and functionalization of an unsymmetrical heterobinuclear, two-dot, Fe-Ru molecular QCA cell is described. The solid state structures of trans-RuCl(dppm)(2)(C[triple bond]CFc) (1) (dppm = methylbis(diphenylphosphane), Fc = (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))) and mixed-valence [trans-RuCl(dppm)(2)(C[triple bond]CFc)][BF(4)] (1a) as well as XPS and spectroscopic data suggest class II behavior suitable for the intended application. Utilization of the trans-Cl position of 1 permits functionalization for surface binding. Two "tailed" complexes of 1, trans-Ru(dppm)(2)(C[triple bond]CFc)(C[triple bond]CPhOCH(3)) (2) and trans-[Ru(dppm)(2)(C[triple bond]CFc)(N[triple bond]CCH(2)CH(2)NH(2))][PF(6)] (3), have been prepared and characterized. The solid state structure of 3 and multinuclear NMR experiments define the structures. In addition, the spectroscopic properties of all complexes and their mixed-valence species are used to define the effect of the substituent "tail" on mixed-valence properties. Further, the electrochemistry of these compounds permits assessment of the extent of perturbation of the substituents on the comproportionation constants and overall electrochemical stability. The complexes possess properties necessary for candidate QCA molecules.     

Computational analyses of singlet-singlet and singlet-triplet transitions in mononuclear gold-capped carbon-rich conjugated complexes

Density functional theory and CASSCF calculations have been used to determine equilibrium geometries and vibrational frequencies of metal-capped one-dimensional pi-conjugated complexes (H3P)Au(C[triple chemical bond]C)(n)(Ph) (n = 1-6), (H3P)Au(C[triple chemical bond]CC6H4)(C[triple chemical bond]CPh), and H3P--Au(C[triple chemical bond]CC6H4)C[triple chemical bond]CAu--PH3 in their ground states and selected low-lying pi(pi)* excited states. Vertical excitation energies for spin-allowed singlet-singlet and spin-forbidden singlet-triplet transitions determined by the time-dependent density functional theory show good agreement with available experimental observations. Calculations indicate that the lowest energy 3(pi(pi)*) excited state is unlikely populated by the direct electronic excitation, while the low-lying singlet and triplet states, slightly higher in energy than the lowest triplet state, are easily accessible by the excitation light used in experiments. A series of radiationless transitions among related excited states yield the lowest 3(pi(pi)*) state, which has enough long lifetimes to exhibit its photochemical reactivities.     

Synthesis, photophysics, electrochemistry, theoretical, and transient absorption studies of luminescent copper(I) and silver(I) diynyl complexes. X-ray crystal structures of [Cu3(micro-dppm)3(micro3-eta1-C triple bond CC triple bond CPh)2]PF6 and [Cu3(micro-dppm)3(micro3-eta1-C triple bond CC triple bond CH)2]PF6

A series of soluble trinuclear copper(I) and silver(I) complexes containing bicapped diynyl ligands, [M(3)(micro-dppm)(3)(micro(3)-eta(1)-C triple bond CC triple bond CR)(2)]PF(6) (M = Cu, R = Ph, C(6)H(4)-CH(3)-p, C(6)H(4)-OCH(3)-p, (n)C(6)H(13), H; M = Ag, R = Ph, C(6)H(4)-OCH(3)-p), has been synthesized and their electronic, photophysical, and electrochemical properties studied. The X-ray crystal structures of [Cu(3)(micro-dppm)(3)(micro(3)-eta(1)-C triple bond CC triple bond CPh)(2)]PF(6) and [Cu(3)(micro-dppm)(3)(micro(3)-eta(1)-C triple bond CC triple bond CH)(2)]PF(6) have been determined.     

Platinum(II) 1,10-phenanthroline complexes of acetylides containing redox-active groups

The new diimine ligand 3,8-di-n-pentyl-4,7-di(phenylethynyl)-1,10-phenanthroline (1) was used for the synthesis of a range of Pt(II) complexes, viz.[Pt(1)Cl2], [Pt(1)(C triple bond C-Ph)2], [Pt(1)(C triple bond C-Fc)2] and [Pt(1)(C triple bond C-p-C6H4-C triple bond C-Fc)2](Fc = ferrocenyl). Crystal structure analyses were performed for [Pt(1)Cl2] and [Pt(1)(C triple bond C-Ph)2] and revealed that the di(acetylide)pi-tweezer of the latter binds a molecule of chloroform through C-H...pi hydrogen bonds. The redox and optical properties of 1 and its complexes were investigated by (spectro-)electrochemistry, UV-Vis and luminescence spectroscopy, and an energy level diagram was derived for [Pt(1)(C triple bond C-Fc)2] and related compounds on the basis of the data collected. The ferrocenyl-substituted Pt(II) complexes are donor-sensitiser assemblies. Intramolecular quenching of the photoexcited Pt(II) diimine unit leads to very short luminescence lifetimes for [Pt(1)(C triple bond C-p-C(6)H(4)-C triple bond C-Fc)2](2 ns) and [Pt(1)(C triple bond C-Fc)2](0.3 ns), as opposed to [Pt(1)(C triple bond C-Ph)2](0.7 micros). Excimer formation has been observed for [Pt(1)(C triple bond C-Ph)(2)] at room temperature in dichloromethane and at low temperatures in frozen glassy dichloromethane and 2-methyltetrahydrofuran solution, but not in the solid state.