Molecular Engineering of Ruthenium-based Photosensitizers with Superior Photovoltaic Performance in DSSC: Novel N-Alkyl 2-Phenylindole-based Ancillary Ligands

In this work, we report the design and successful synthesis of two new heteroleptic polypyridyl Ru(II) complexes (SD-5 and SD-6), by incorporating hetero-aromatic electron-donating N-alkyl-2-phenylindole moieties into the ancillary ligand....

Recent Investigations on Thiocyanate-Free Ruthenium(II) 2,2′-Bipyridyl Complexes for Dye-Sensitized Solar Cells

Three decades ago, dye-sensitized solar cells (DSSCs) emerged as a method for harnessing the energy of the sun and for converting it into electricity. Since then, a lot of work has been devoted to create better global photovoltaic efficiencies and long term stability. Among photosensitizers for DSSCs, thiocyanate-free ruthenium(II) complexes have gained increasing interest due to their better stability compared to conventional thiocyanate-based complexes, such as benchmark dyes N719 and Z907. In this mini-review, two classes of thiocyanate-free Ru(II) complexes are presented: (a) bis-bipyridyl compounds bearing an ancillary cyclometalating bidentate ligand; (b) bipyridyl compounds bearing non-cyclometalating ancillary ligands. The coverage, mainly from 2014 up to now, is not exhaustive, but illustrates the most recent design strategies and photovoltaic properties of these two families of ruthenium(II) dyes.

Applicability of Reddish Orange Light Emitting Samarium (III) Complexes For Biomedical and Multifunctional Optoelectronic Devices

Six crimson samarium (III) complexes based on β-ketone carboxylic acid and ancillary ligands were synthesized by adopting grinding technique. All synthesized complexes were investigated via employing elemental analysis, infrared, UV-Vis, NMR, TG/DTG and photoluminescence studies. Optical properties of these photostimulated samarium (III) complexes exhibit reddish-orange luminescence due to 4G5/2→6H7/2 transition at 606 nm of samarium (III) ions. Further, energy band gap, color purity, CIE color coordinates, CCT and quantum yield of all complexes were determined accurately. Replacement of water molecules by ancillary ligands enriched the complexes (S2-S6) with decay time, quantum yield, luminescence, energy band gap and biological properties than parent complex (S1). Interestingly, these efficient properties of complexes may find their applications in optoelectronic and lighting systems. In addition to these the antioxidant and antimicrobial assays were also investigated to explore the application in biological assays.

Synthesis and Reactivity of Group 12 β-Diketiminate Coordination Complexes

<p>The variable β-diketiminate ligand poses as a suitable chemical environment to explore unknown reactivity and functionality of metal centres. Variants on the β-diketiminate ligand can provide appropriate steric and electronic stabilization to synthesize a range of β-diketiminate group 12 metal complexes. This project aimed to explore various β-diketiminate ligands as appropriate ancillary ligands to derivatise group 12 element complexes and investigate their reactivity. A β-diketiminato-mercury(II) chloride, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]HgCl, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to mercury dichloride. Attempts to derivatise the β-diketiminato-mercury(II) chloride using salt metathesis reactions were unsuccessful with only β-diketiminate ligand degradation products being observed in the ¹H NMR. A β-diketiminato-cadmium chloride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdCl, was derivatized to a β-diketiminato-cadmium phosphanide, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]Cd P(C₆H₁₁)₂, via a lithium dicyclohexyl phosphanide and a novel β-diketiminato-cadmium hydride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdH, via Super Hydride. Initial reactivity studies of the novel cadmium hydride with various carbodiimides yielded a β-diketiminato-homonuclear cadmium-cadmium dimer, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂Cd]₂, which formed via catalytic reduction of the cadmium hydride. Attempts to synthesize an amidinate insertion product via a salt metathesis reaction or a ligand exchange reaction proved unsuccessful but a novel cadmium amidinate, [{CH(N-C₆H₁₁)₂}₂{CH(N-C₆H₁₁)(N(H)-C₆H₁₁)}Cd], was synthesized from addition of dicyclohexyl formamidine to bis-hexamethyldisilazane cadmium. A β-diketiminato-zinc(II) bromide, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]ZnBr, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to zinc dibromide. The β-diketiminato-zinc(II) bromide was derivatized to a variety of complexes (including amides and phosphanides) by a salt metathesis reaction. Chalcogen addition reactions were performed from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₁₁)₂] to produce double addition products from sulfur, selenium and tellurium. Chalcogen addition reactions from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₅)₂] produced a double addition product for selenium and a β-diketiminato-zinc(II) tellunoite bridged dimer, [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}Zn]Te, from tellurium. A total of 14 compounds were characterized via X-ray diffraction. Photoluminescence studies of the β-diketiminato-zinc(II) compounds were conducted where it was proposed that an electron transfer from the lone pair on the hetero-atom influenced the quantum yield and fluorescence intensities.</p>

Synthesis and Reactivity of Group 12 β-Diketiminate Coordination Complexes

<p>The variable β-diketiminate ligand poses as a suitable chemical environment to explore unknown reactivity and functionality of metal centres. Variants on the β-diketiminate ligand can provide appropriate steric and electronic stabilization to synthesize a range of β-diketiminate group 12 metal complexes. This project aimed to explore various β-diketiminate ligands as appropriate ancillary ligands to derivatise group 12 element complexes and investigate their reactivity. A β-diketiminato-mercury(II) chloride, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]HgCl, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to mercury dichloride. Attempts to derivatise the β-diketiminato-mercury(II) chloride using salt metathesis reactions were unsuccessful with only β-diketiminate ligand degradation products being observed in the ¹H NMR. A β-diketiminato-cadmium chloride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdCl, was derivatized to a β-diketiminato-cadmium phosphanide, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]Cd P(C₆H₁₁)₂, via a lithium dicyclohexyl phosphanide and a novel β-diketiminato-cadmium hydride, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂]CdH, via Super Hydride. Initial reactivity studies of the novel cadmium hydride with various carbodiimides yielded a β-diketiminato-homonuclear cadmium-cadmium dimer, [CH{(CH₃)CN-2,6-iPr₂C₆H₃}₂Cd]₂, which formed via catalytic reduction of the cadmium hydride. Attempts to synthesize an amidinate insertion product via a salt metathesis reaction or a ligand exchange reaction proved unsuccessful but a novel cadmium amidinate, [{CH(N-C₆H₁₁)₂}₂{CH(N-C₆H₁₁)(N(H)-C₆H₁₁)}Cd], was synthesized from addition of dicyclohexyl formamidine to bis-hexamethyldisilazane cadmium. A β-diketiminato-zinc(II) bromide, [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]ZnBr, was synthesized by addition of [o-C₆H₄{C(CH₃)=N-2,6- iPr₂C₆H₃}{NH(2,6- iPr₂C₆H₃)}]Li to zinc dibromide. The β-diketiminato-zinc(II) bromide was derivatized to a variety of complexes (including amides and phosphanides) by a salt metathesis reaction. Chalcogen addition reactions were performed from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₁₁)₂] to produce double addition products from sulfur, selenium and tellurium. Chalcogen addition reactions from [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}ZnP(C₆H₅)₂] produced a double addition product for selenium and a β-diketiminato-zinc(II) tellunoite bridged dimer, [o-C₆H₄{C(CH₃)=N-2,6-iPr₂C₆H₃}{NH(2,6-iPr₂C₆H₃)}Zn]Te, from tellurium. A total of 14 compounds were characterized via X-ray diffraction. Photoluminescence studies of the β-diketiminato-zinc(II) compounds were conducted where it was proposed that an electron transfer from the lone pair on the hetero-atom influenced the quantum yield and fluorescence intensities.</p>

Synthesis and Study of the Physical and Photovoltaic Properties of Novel Heteroleptic Ruthenium(II) Complexes Ligated with Highly π-Conjugated Bipyridine Ancillary and Phenanthroline Anchoring Ligand for Dye-Sensitized Solar Cells

Six new heteroleptic ruthenium(II) complexes (JM1–JM6), each bearing a highly π-conjugated bipyridine ancillary ligand (a methoxy-substituted analog (L1) and a phenanthroline-type anchoring ligand (L2) (dcphen or dcvphen; [Ru(L)2(NCS)2][TBA]2; L1 = 4,4′-bis{2-(3,4-dimethoxyphenyl)ethenyl}-2,2′-bipyridine (dmpbpy), 4,4′-bis{2-(1,1′-biphenyl)-4-ylethenyl}-2,2′-bipyridine (bpbpy), or 4,4′-bis{2-(4′-methoxy-[1,1′-biphenyl]-4-ylethenyl}-2,2′-bipyridine (mbpbpy); L2 = 4,7-dicarboxy-1,10-phenanthroline (dcphen) or 4,7-bis(E-carboxyvinyl)-1,10-phenanthroline (dcvphen)) were synthesized, and their physical and photovoltaic properties were investigated. Various dye-sensitized solar cells (DSSCs) were fabricated using heteroleptic ruthenium(II) complexes. Ruthenium(II) complex JM1, ligated to dmpbpy (ancillary) and dcphen (anchoring) ligands, exhibited the maximum power conversion efficiency (PCE) value of 3.40%, which was approximately 71% of the efficiency exhibited by the commercially available N719-sensitized solar cells. Ruthenium(II) complex JM5, ligated to mbpbpy (ancillary) and dcphen (anchoring) ligands, exhibited the second-best PCE value (2.52%), and ruthenium(II) complex JM3, ligated to bpbpy (ancillary) and dcphen (anchoring) ligands, exhibited a PCE value of 1.45%. It was observed that the PCE values of the DSSCs could be significantly improved by introducing the electron-donating methoxy group at proper positions of the ancillary ligands present in the heteroleptic ruthenium(II) complexes (such as JM1 and JM5).

Theoretical Study on Ethylene Polymerization Catalyzed by Half-Titanocenes Bearing Different Ancillary Groups

Half-titanocenes are well known to show high activity for ethylene polymerization and good capability for copolymerization of ethylene with other olefins, and the ancillary ligands can crucially affect the catalytic performance. In this paper, the mechanisms of ethylene polymerization catalyzed by three half-metallocenes, (η5-C5Me5)TiCl2(O-2,6-iPr2C6H3) (1), (η5-C5Me5)TiCl2(N=CtBu2) (2) and [Me2Si(η5-C5Me4)(NtBu)]TiCl2 (3), have been investigated by density functional theory (DFT) method. At the initiation stage, a higher free energy barrier was determined for complex 1, probably due to the presence of electronegative O atom in phenoxy ligand. At the propagation stage, front-side insertion of the second ethylene is kinetically more favorable than back-side insertion for complexes 1 and 2, while both side insertion orientations are comparable for complex 3. The energy decomposition showed that the bridged cyclopentadienyl amide ligand could enhance the rigidity of the active species as suggested by the lowest deformation energy derived from 3. At the chain termination stage, β-H transfer was calculated to be a dominant chain termination route over β-H elimination, presumably owing to the thermodynamic perspective.