Herein, we synthesized Sb-based single crystals (SCs) of Cs2AgSbCl6 with an impressive low bandgap of ∼1.82 eV and demonstrated the effect of strain on optical properties. Interestingly, the polycrystalline ground powder and the heated SCs of Cs2AgSbCl6 exhibited a larger bandgap of ∼2.55 eV. The reduction of bandgap is attributed to the existence of strain in the SC as confirmed by X-ray diffraction and Raman spectroscopy and supported by density functional theory (DFT) calculations. The strain engineering for bandgap reduction can play a pivotal role for developing low-bandgap lead-free double perovskite for environmentally friendly solar cell applications.

A donor-acceptor dyad model system using a flavin moiety as a photo-active acceptor has been synthesized for an energy and photo-induced electron transfer study. The photophysical investigations of the dyad revealed a multi-path energy and electron transfer process with a very high transfer efficiency. The photo-activity of flavin was believed to play an important role in the process, implying the potential application of flavin as a novel acceptor molecule for photovoltaics.

The reaction of a dinucleating bis(iminopyridine) ligand L bearing a xanthene linker (L = N,N'-(2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene-4,5-diyl)bis(1-(pyridin-2-yl)methanimine)) with Ni(COD)(DPA) (COD = cyclooctadiene, DPA = diphenylacetylene) leads to the formation of a new dinuclear complex Ni(L)(DPA). Ni(L)(DPA) can also be obtained in a one-pot reaction involving Ni(COD), DPA and L. The X-ray structure of Ni(L)(DPA) reveals two square-planar Ni centers bridged by a DPA ligand. DFT calculations suggest that this species features Ni centers antiferromagnetically coupled to each other and their iminopyridine ligand radicals. Treatment of Ni(L)(DPA) with one equivalent of ethyl propiolate (HCCCOEt) forms the Ni(L)(HCCCOEt) complex. Addition of the second equivalent of ethyl propiolate leads to the observation of cyclotrimerised products by H NMR spectroscopy. Carrying out the reaction under catalytic conditions (1 mol% of Ni(L)(DPA), 24 h, room temperature) transforms 89% of the substrate, forming primarily benzene products (triethyl benzene-1,2,4-tricarboxylate and triethyl benzene-1,3,5-tricarboxylate) in 68% yield, in a ca. 5 : 1 relative ratio. Increasing catalyst loading to 5 mol% leads to the full conversion of ethyl propiolate to benzene products; no cyclotetramerisation products were observed. In contrast, the reaction is significantly more sluggish with methyl propargyl ether. Using 1 mol% of the catalyst, only 25% conversion of methyl propargyl ether was observed within 24 h at room temperature. Furthermore, methyl propargyl ether demonstrates the formation of cyclooctatetraenes in significant amounts at a low catalyst concentration, whereas a higher catalyst concentration (5 mol%) leads to benzene products exclusively. Density functional theory was used to provide insight into the reaction mechanism, including structures of putative dinuclear metallocyclopentadiene and metallocycloheptatriene intermediates.

The dinuclear complex Ni(2)L(1)(η(2)-CS(2))(2) (2), featuring iminopyridine ligation, is prepared by COD substitution from Ni(2)L(1)(COD)(2) (1). Spectroscopic, structural, and theoretical data reveals significant activation of the metal-bound C-S bonds, as well as the different oxidation states of the iminopyridine in (1-) and (0).

We are developing bimetallic platforms for the cooperative activation of heteroallenes. Toward this goal, we designed a new family of bis(iminopyridine) ((N,N′-1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) and N,N′-1,1′-(1,4-phenylene)bis(N-(1-(pyridin-2-yl)ethylidene)methanamine)) dinickel complexes, synthesized their CS2 compounds, and studied their reactivity. Bis(iminopyridine) ligands L react with Ni(COD)2 to form Ni2(L)2 complexes or Ni2(L)(COD)2 complexes as a function of the steric and electronic properties of the ligand precursor. Product structures disclosed an anti geometry in the Ni2(L)(COD)2 species and helical (anti) structures for Ni2(L)2 complexes. Carbon disulfide adducts Ni2(L)(CS2)2 were obtained in good yields upon addition of CS2 to Ni2(L)(COD)2 or in a one-pot reaction of L with 2 equiv of both Ni(COD)2 and CS2. Ni2(L)(CS2)2 complexes are highly flexible, displaying both syn and anti conformations (shortest S- - -S separations of 5.0 and 9.5 Å, respectively) in the solid state. DFT calculations demonstrate virtually no energy difference between the two conformations. Electrochemical studies of the Ni2(L)(CS2)2 complexes displayed two ligand-based reductions and a broad CS2-based oxidation. Chemical oxidation with [FeCp2]+ liberated free CS2. The addition of NHC (NHC = 1,3-di-tert-butylimidazolin-2-ylidene) to Ni2(L)(CS2)2 yielded Ni2(NHC)2(CS2)2, in which both carbon disulfide ligands are bridging two Ni centers.