新型氮杂环卡宾银(Ⅰ)配合物的合成及其晶体结构

以取代苄氯(1a~1c)为起始原料,与咪唑经氮烷基化反应制得苄基咪唑氯盐(2a~2c);2a~2c与氧化银经原位去质子化反应合成了3种新型的氮杂环卡宾银配合物——(NHC)AgCl[NHC:1,3-二(4-甲氧基苄基)咪唑-2-亚基(3a),1,3-二(3-甲氧基苄基)咪唑-2-亚基(3b)]和[(NHC)AgCl]_2[NHC=1,3-二(4-氯苄基)咪唑-2-亚基(3c)],其结构经~1H NMR,~(13)C NMR,IR,元素分析和X-射线单晶衍射表征。3a~3c单晶结构均属单斜晶系,3a为P21/n空间群,3b和3c为P21/c空间群,3a和3b为单核银配合物,3c为双核银配合物。     

新型氮杂环卡宾银(I)配合物的合成及其晶体结构

以取代苄氯(1a~1c)为起始原料,与咪唑经氮烷基化反应制得苄基咪唑氯盐(2a~2c); 2a~2c与氧化银经原位去质子化反应合成了3种新型的氮杂环卡宾银配合物--(NHC)AgCl［NHC: 1,3-二(4-甲氧基苄基)咪唑-2-亚基(3a), 1,3-二(3-甲氧基苄基)咪唑-2-亚基(3b)］和［(NHC)AgCl]₂［NHC=1,3-二(4-氯苄基)咪唑-2-亚基(3c)］,其结构经¹H NMR, ¹³C NMR, IR,元素分析和X-射线单晶衍射表征。3a~3c单晶结构均属单斜晶系,3a为P2₁/n空间群,3b和3c为P2₁/c空间群,3a和3b为单核银配合物,3c为双核银配合物。     

基于1-(2-吡啶甲基)-1,2,4-三唑的金属有机化合物的合成及反应研究(英文)

合成了1-(2-吡啶甲基)-1,2,4-三唑(L)并研究了其与有机锡和羰基钼(钨)的配位反应,合成了通过三唑4位氮原子以单齿形式配位的有机锡衍生物L2SnR2Cl2(R=Me,n-Bu或Ph)和羰基金属配合物LM(CO)5(M=Mo或W),以及N,N螯合双齿配位的四羰基金属配合物LM(CO)4。当用氯化苄处理L时,制得了相应的三唑盐,该盐用氧化银处理后与M(CO)5THF或M(CO)4(NHC5H10)2(NHC5H10为哌啶)反应,得到了基于三唑的氮杂环卡宾衍生物L′M(CO)5和L′M(CO)4(L′=1-(2-吡啶甲基)-4-苄基-1,2,4-三唑-5-碳烯)。X-射线单晶衍射分析表明,在L′M(CO)5中氮杂环卡宾配体L′表现为通过卡宾碳配位的单齿配体;而在L′M(CO)4中,L′表现为通过卡宾碳和吡啶氮原子配位的螯合[C,N]双齿配体。     

过渡金属N-杂环卡宾配合物合成*

由于N-杂环卡宾配体（NHCs）的独特性能,N-杂环卡宾过渡金属配合物在均相催化等方面取得了重要应用,但是其合成方法却发展缓慢。本文综述了N-杂环卡宾过渡金属配合物合成方法的最新研究进展,介绍了富电子烯烃裂解反应、游离NHC直接配位反应、配体底物的脱质子原位反应、卡宾加合物热解反应、金属交换转移反应和C2-X（X为甲基、卤原子或氢原子）键氧化加成反应等合成N-杂环卡宾过渡金属配合物的主要方法,此外本课题组还首次发现了金属粉末法,该法可用于规模化合成铁、钴、镍、铜等第一过渡系金属NHC配合物。     

多咪唑盐合成的N-杂环卡宾金属配合物研究进展

N-杂环卡宾金属配合物具有良好的化学稳定性和催化活性,一直是有机化学研究领域中的热点.咪唑盐作为N-杂环卡宾的前体,其制备容易,结构多样的特点为构建拓扑结构的N-杂环卡宾金属配合物提供了基础.主要针对近年来由环状多咪唑盐、非环状多咪唑盐为配体与金属进行组装,或以咪唑盐与P/N配体与金属共同组装,或经过异腈分布合成法形成的具有特殊柱状、笼状、环状、"分子方"和"分子矩形"等结构的多N-杂环卡宾金属配合物的合成,结构及物理化学性质进行归纳总结,并对其研究前景进行了展望.     

路易斯碱稳定的氢化硅亚胺:二胺基氯硅烷与氮杂环卡宾的反应性研究

硅亚胺作为亚胺的重元素类似物,是一类重要的含硅多重键化合物.本研究首次报道了氮杂环卡宾诱导下二胺基氯硅烷脱除Me3Si Cl来制备硅亚胺的方法.合成了二胺基氯硅烷[Ar N(Si Me_3)]_2SiHCl(2)(Ar=2,6-i-Pr_2C_6H_3),通过~1H NMR,~(13)C NMR,~(29)Si NMR,红外以及元素分析的表征确定了2的结构.研究了2与不同位阻氮杂环卡宾的反应性,发现其与位阻较大的1,3-二叔丁基咪唑-2-亚基(It Bu)和1,3-二异丙基-4,5-二甲基咪唑-2-亚基(Ii Pr)均不反应,但是其与位阻较小的1,3,4,5-四甲基咪唑-2-亚基(IMe_4)反应生成氢化硅亚胺3.     

基于Cyclam衍生物的单核金属配合物的结构及核酸酶活性

以1,8-二甲基-1,4,8,11-四氮杂环十四烷为原料,以N,N′-二叔丁氧羰基-2-甲璜酰氧基-1,3-二氨基丙烷为烷基化试剂,合成了cyclam衍生物:1,8-二(N,N′-二叔丁氧羰基-1,3-二氨基异丙基)-4,11-二甲基-1,4,8,11-四氮杂环十四烷(L1);及其对应的系列单核金属配合物,Zn(L1)Cl2(1),Ni(L1)Cl2(2)和Cu(L1)Cl2(3);核磁结果表明,L1为C2对称结构,且cyclam环上每一个亚甲基碳上的2个氢化学不等价;利用2D[1H,15N]HSQC对比配体配位前后N-H化学位移的变化,确定配合物的结构是金属与配体cyclam环上的4个氮原子配位;利用变温核磁1H NMR和13C NMR,结合2D[1H,15N]HSQC核磁共振波谱表明,配合物1在溶液中主要以两种构型并存,并主要以trans-Ⅲ构型存在。此外,用凝胶电泳研究了配体与单核金属配合物对超螺旋p BR322质粒DNA切割活性;实验结果表明,配合物3在抗坏血酸存在的条件下具有核酸酶活性,而配体(L1),配合物1和配合物2在实验条件下,无论是氧化切割还是水解切割都显阴性。     

铜催化的硅烷还原酰基叠氮的反应研究

本文报道了铜催化的硅烷还原酰基叠氮的反应。考察了多种CuCl_n/NHC·HCl(n=1,2;NHC=N-杂环卡宾)催化剂前体和不同的硅烷的组合体系。筛选确定了最有效率的CuCl/IPr·HCl(IPr=N,N'-双(2,6-二异丙基苯基)咪唑-2-亚基)作为催化前体和使用(EtO)_3SiH作为还原试剂为最优条件。该方法原料及催化剂廉价易得,反应条件温和,效率高。具有良好的化学选择性和官能团耐受性,能以较高的产率得到多种不同类型的甲酰胺,是还原酰基叠氮以制备甲酰胺类化合物的高效的新方法。所有的产物均进行了~1H NMR和~(13)C NMR核磁共振表征。     

绿色磷光四配位氮杂环卡宾铜(Ⅰ)配合物的合成及发光性质

为了制备发光性能优良的新型四配位氮杂环卡宾铜髣配合物,以咪唑、苯并咪唑、2-溴-5-氟-6-甲基吡啶和溴化苄为初始原料,反应生成氮杂环卡宾配体(Ph-Im-flumePy)PF_6和(Ph-BenIm-mePy)PF_6,随后卡宾配体与Cu粉及配体双(2-二苯基膦)苯醚(POP)反应,制备出2个四配位类型的氮杂环卡宾铜髣配合物[Cu(Ph-Im-flumePy)(POP)]PF_6(P1)和[Cu(Ph-BenIm-flumePy)(POP)]PF_6(P2)。通过核磁、质谱技术对产物结构进行了表征。系统研究了配合物的紫外-可见吸收光谱、发射光谱以及发光寿命等光学特性。结果表明,配合物P1和P2的最低吸收峰分别位于325和335 nm处。粉末状态下,配合物P1在514 nm处有较强的绿光发射,量子发光效率为82.6%,激发态寿命为56μs;而配合物P2的波长在516 nm处,量子发光效率为49.2%,激发态寿命为50.6μs。在PMMA(10%,w/w)膜片中,配合物P1的发射波长蓝移至505 nm处,激发态寿命为40.7μs,量子发光效率为38.0%;而配合物P2的发射波长位于508 nm处,激发态寿命为61μs,量子发光效率为44.2%。     

螯合型氮杂环卡宾金属化合物的研究进展

氮杂环卡宾金属化合物已被广泛应用于有机、材料、医药及生物科学等领域.从金属化合物的结构出发,主要介绍含NHC⌒P、NHC⌒N、NHC⌒O和NHC⌒S配体螯合型金属化合物的合成及应用,综述了近年来基于氮杂环卡宾的螯合型金属化合物合成与应用的最新研究进展.     

Controlled synthesis of nickel(II) dihalides bearing two different or identical N-heterocyclic carbene ligands and the influence of carbene ligands on their structures and catalysis

Ni(II) dihalides bearing two different or identical NHC ligands have been prepared via a controlled indene elimination synthesis, and the former product provides a new route for the design of biscarbene Ni(II)-based catalysts. The indene elimination reaction of the indenynickel(II) complex (1-H-Ind)Ni(NHC)X (Ind = indenyl) with one equiv. of a distinct imidazolium salt at 100 °C afforded the first example of Ni(II) dihalides bearing two different NHC ligands, i.e., Ni(iPr)(IPr)X(2) [iPr = 1,3-diisopropylimidazol-2-ylidene, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), X = Cl, 1; X = Br, 2] and Ni(iPr)(IMes)Br(2) [IMes = 1,3-bis(mesityl)imidazol-2-ylidene, 3]. Alternatively, complexes 1-3 can be synthesized using a bis-indenyl Ni(II) complex (1-H-Ind)(2)Ni as starting materials via a step-by-step indene elimination at different reaction temperatures. The direct reaction of (1-R-Ind)(2)Ni (R = H or Me) with two equiv. of imidazolium salts at 100 °C afforded Ni(II) dihalides bearing two identical NHC ligands, i.e., Ni(iPr)X(2) (X = Cl, 4; X = Br, 5) and Ni(IPr)Cl(2) (6). All of these complexes were characterized by elemental analysis, NMR spectroscopy and X-ray crystallography for complexes 1-5. The two identical or different NHC ligands in complexes 1-6 changed the coordination sphere of the nickel center from a typical square-planar geometry to a slightly tetrahedral array. A preliminary catalytic study on the cross-coupling reactions of aryl Grignard reagents with aryl halides revealed that complexes 1 and 2 possess the highest activity. In comparison, complexes 3 and 6 exhibited moderate activity and the least active complexes were 4 and 5.     

1,3-dialkyl- and 1,3-diaryl-3,4,5,6-tetrahydropyrimidin-2-ylidene rhodium(i) and palladium(II) complexes: synthesis, structure, and reactivity

The synthesis of novel 1,3-diaryl- and 1,3-dialkylpyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and their rhodium(i) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (7), bromo(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (8) (cod=eta(4)-1,5-cyclooctadiene, mesityl=2,4,6-trimethylphenyl), chloro(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (9), and chloro(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (10) were prepared by reaction of [[Rh(cod)Cl](2)] with lithium tert-butoxide followed by addition of 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium bromide (3), 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (4), 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium bromide (6), and 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P2(1)/n, and 8 in the monoclinic space group P2(1). Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (11), and dicarbonylchloro[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (12). The wavenumbers nu(CO I)/nu(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/1976 and 2063/1982 cm(-1), respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(i) bis-NHC complexes [Ag(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]AgBr(2) (13) and [Ag[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene](2)]AgBr(2) (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2) (2+)(Ag(2)Br(2)Cl(4) (4-))(1/2) (15) and Pd[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]Cl(2) (16). Complex 15 crystallizes in the monoclinic space group P2(1)/c, and 16 in the monoclinic space group C(2)/c. The catalytic activity of 15 and 16 in Heck-type reactions was studied in detail. Both compounds are highly active in the coupling of aliphatic and aromatic vinyl compounds with aryl bromides and chlorides with turnover numbers (TONs) up to 2000000. Stabilities of 15 and 16 under Heck-couplings conditions were correlated with their molecular structure. Finally, selected kinetic data for these couplings are presented.     

Stoichiometric and catalytic reactivity of the N-heterocyclic carbene ruthenium hydride complexes [Ru(NHC)(L)(CO)HCl] and [Ru(NHC)(L)(CO)H(eta2-BH4)] (L=NHC, PPh3)

Thermolysis of [Ru(AsPh3)3(CO)H2] with the N-aryl heterocyclic carbenes (NHCs) IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) or the adduct SIPr.(C6F5)H (SIPr=1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene), followed by addition of CH2Cl2, affords the coordinatively unsaturated ruthenium hydride chloride complexes [Ru(NHC)2(CO)HCl] (NHC=IMes , IPr , SIPr ). These react with CO at room temperature to yield the corresponding 18-electron dicarbonyl complexes . Reduction of and [Ru(IMes)(PPh3)(CO)HCl] () with NaBH4 yields the isolable borohydride complexes [Ru(NHC)(L)(CO)H(eta2-BH4)] (, L=NHC, PPh3). Both the bis-IMes complex and the IMes-PPh3 species react with CO at low temperature to give the eta1-borohydride species [Ru(IMes)(L)(CO)2H(eta1-BH4)] (L=IMes , PPh3), which can be spectroscopically characterised. Upon warming to room temperature, further reaction with CO takes place to afford initially [Ru(IMes)(L)(CO)2H2] (L=IMes, L=PPh3) and, ultimately, [Ru(IMes)(L)(CO)3] (L=IMes , L=PPh3). Both and lose BH3 on addition of PMe2Ph to give [Ru(IMes)(L)(L')(CO)H2](L=L'=PMe2Ph; L=PPh3, L'=PMe2Ph). Compounds and have been tested as catalysts for the hydrogenation of aromatic ketones in the presence of (i)PrOH and H2. For the reduction of acetophenone, catalytic activity varies with the NHC present, decreasing in the order IPr>IMes>SIMes.     

Anhydrous TEMPO-H: reactions of a good hydrogen atom donor with low-valent carbon centres

In this paper, we report a novel synthesis of anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H). An X-ray crystal structure and full characterization of the compound are included. Compared to hydrated TEMPO-H, its anhydrous form exhibits improved stability and a differing chemical reactivity. The reactions of anhydrous TEMPO-H with a variety of low-valent carbon centres are described. For example, anhydrous TEMPO-H was reacted with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), an unsaturated NHC. Crystals of [CHNC(6)H(2)(CH(3))(3)](2)C···HO(NC(5)H(6)(CH(3))(4)), IMes···TEMPO-H, were isolated and a crystal structure determined. The experimental structure is compared to the results of theoretical calculations on the hydrogen-bonded dimer. Anhydrous TEMPO-H was also reacted with the saturated NHC, 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), giving the product [CH(2)Ni-Pr(2)C(6)H(3)](2)CH···O(NC(5)H(6)(CH(3))(4)). In contrast, the reaction of hydrated TEMPO-H with 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene gave small amounts of the hydrolysis product, N-(2,6-diisopropylphenyl)-N-[2-(2,6-diisopropylphenylamino)ethyl]formamide. Finally, anhydrous TEMPO-H was reacted with (triphenylphosphoranylidene)ketene to generate Ph(3)PC(H)C(=O)O(NC(5)H(6)(CH(3))(4)). A full characterization of the product, including an X-ray crystal structure, is described.     

The reactivity of N-heterocyclic carbenes and their precursors with [Ru(3)(CO)(12)

The ambient temperature reaction of the N-heterocyclic carbenes (NHCs) 1,3-dimesitylimidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp) with the triruthenium cluster [Ru(3)(CO)(12)], in a 3 : 1 stoichiometric ratio, results in homolytic cleavage of the cluster to quantitatively afford the complexes [Ru(CO)(4)(NHC)] (; NHC = IMes, ; NHC = IDipp). Reaction of the 2-thione or hydrochloride precursors to IMes, i.e. S[double bond, length as m-dash]IMes and IMes.HCl, with the same triruthenium cluster affords the complexes [Ru(4)(mu(4)-S)(2)(CO)(9)(IMes)(2)] () and [Ru(4)(mu(4)-S)(CO)(10)(IMes)(2)] () (3 : 1 and 2 : 1 reaction), and [{Ru(mu-Cl)(CO)(2)(IMes)}(2)] () (3 : 1 reaction) respectively. By contrast, the complex [Ru(3)(mu(3)-S)(2)(CO)(7)(IMeMe)(2)] (), where IMeMe is 1,3,4,5-tetramethylimidazol-2-ylidene, is the sole product of the 2 : 1 stoichiometric reaction of S[double bond, length as m-dash]IMeMe with [Ru(3)(CO)(12)]. Compounds -, and have been structurally characterised by single crystal X-ray diffraction.     

Syntheses, crystal structures, reactivity, and photochemistry of gold(III) bromides bearing N-heterocyclic carbenes

Gold(I) complexes bearing N-heterocyclic carbenes (NHC) of the type (NHC)AuBr (3a/3b) [NHC = 1-methyl-3-benzylimidazol-2-ylidene (= MeBnIm), and 1,3-dibenzylimidazol-2-ylidene (= Bn(2)Im)] are prepared by transmetallation reactions of (tht)AuBr (tht = tetrahydrothiophene) and (NHC)AgBr (2a/2b). The homoleptic, ionic complexes [(NHC)(2)Au]Br (6a/6b) are synthesized by the reaction with free carbene. Successive oxidation of 3a/3b and 6a/6b with bromine gave the respective (NHC)AuBr(3) (4a/4b) and [(NHC)(2)AuBr(2)]Br (7a/7b) in good overall yields as yellow powders. All complexes were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. Reactions of the Au(III) complexes towards anionic ligands like carboxylates, phenolates and thiophenolates were investigated and result in a complete or partial reduction to a Au(I) complex. Irradiation of the Au(III) complexes with UV light yield the Au(I) congeners in a clean photo-reaction.     

Carbene-pyridine chelating 2Fe2S hydrogenase model complexes as highly active catalysts for the electrochemical reduction of protons from weak acid (HOAc)

Two asymmetrically disubstituted diiron complexes (micro-pdt)[Fe(CO)(3)][Fe(CO)(eta(2)-L)] (L = 1-methyl-3-(2-pyridyl)imidazol-2-ylidene (NHC(MePy)), 2; 1,3-bis(2-picolyl)imidazol-2-ylidene (NHC(diPic)), 4) and a mono-substituted diiron complex (mu-pdt)[Fe(CO)(3)][Fe(CO)(2)(NHC(diPic))] (3) were prepared as biomimetic models of the Fe-only hydrogenase active site. X-Ray studies show that the NHC(MePy) and NHC(diPic) ligands in 2 and 4 each coordinate to the single iron atom as NHC-Py chelating ligands in two basal positions and the NHC(diPic) ligand of complex 3 lies in an apical position as a monodentate ligand. The large ranges of the highest and the lowest nu(CO) frequencies of 2 and 4 reflect that the relatively uneven electron density on the two iron atoms of the 2Fe2S model complexes 2 and 4 is as that observed for mono-substituted diiron complexes of good donor ligands. The cyclic voltammograms and the electrochemical proton reduction by 2 and 3 were studied in the presence of HOAc to evaluate the effect of asymmetrical substitution of strong donor ligands on the redox properties of the iron atoms and on the electrocatalytic activity for proton reduction.     

两个新型三核镍(Ⅱ)配合物的合成及其晶体结构

5-溴水杨醛和5-氯水杨醛分别与N-环己基-1,2-丙二胺经缩合反应制得Schiff碱配体(L1和L2); L1和L2分别与Ni(Ac)₂·4H₂O经配位反应合成两个新型的三核Schiff碱配合物(1和2),其结构经X-射线单晶衍射表征。1(CCDC: 1 008 203)和2(CCDC: 1 008 204)属单斜晶系,空间群P2₁/c,晶胞参数1：a=9.111(4) , b=12.089(6) , c=18.724(8) , β=92.117(7)°; 2： a=9.346 8(12) , b=11.507 3(15) , c=18.539(2) , β=93.774(2)°。     

Emissive Osmium(II) Complexes Supported by N-Heterocyclic Carbene-based C(∧)C(∧)C-Pincer Ligands and Aromatic Diimines

Osmium(II) complexes containing N-heterocyclic carbene (NHC)-based pincer ligand 1,3-bis(1-methylimidazolin-2-ylidene)phenyl anion (C(1)(∧)C(∧)C(1)) or 1,3-bis(3-methylbenzimidazolin-2-ylidene)phenyl anion (C(2)(∧)C(∧)C(2)) and aromatic diimine (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,4'-diphenyl-2,2'-bipyridine (Ph(2)bpy)) in the form of [Os(C(∧)C(∧)C)(N(∧)N)(CO)](+) have been prepared. Crystal structures for these complexes show that the Os-C(NHC) bonds are essentially single (Os-C(NHC) distances = 2.079(5)-2.103(7) ?). Spectroscopic comparisons and time-dependent density functional theory (TD-DFT) calculations suggest that the lowest-energy electronic transition associated with these complexes (λ(max) = 493-536 nm, ε(max) = (5-10) × 10(3) dm(3) mol(-1) cm(-1), solvent = CH(3)CN) originate from a d(π)(Os(II)) → π*(N(∧)N) metal-to-ligand charge transfer transition, where the d(π)(Os(II)) and π*(N(∧)N) levels contain significant contribution from the C(∧)C(∧)C ligands. All these complexes are emissive in the red-spectral region (674-731 nm) with quantum yields of 10(-4)-10(-2) and emission lifetimes of around 1-6 μs. Transient absorption spectroscopy and spectroelectrochemical measurements have also been used to probe the nature of the emissive excited-states. Overall, this joint experimental and theoretical investigation reveals that the C(∧)C(∧)C ligands can be used to modulate the photophysical properties of a [Os(N(∧)N)] core via the formation of the hybrid [Os + C(∧)C(∧)C] frontier orbitals.