Mononuclear complexes [Os(II)(bpy)2(H2L1)](ClO4)2 ([](ClO4)2) and [Os(II)(bpy)2(H2L2)](ClO4)2 ([](ClO4)2) incorporating two free NH protons at the back face of the coordinated H2L, and deprotonated L(2-) bridged symmetric dinuclear complexes [(bpy)2Os(II)(μ-L1(2-))Os(II)(bpy)2)](ClO4)2 ([](ClO4)2) and [(bpy)2Os(II)(μ-L2(2-))Os(II)(bpy)2)](ClO4)2 ([](ClO4)2) (bpy = 2,2'-bipyridine, H2L1 = 2,2'-biimidazole and H2L2 = 2,2'-bis(4,5-dimethylimidazole)) have been characterised. Crystal structures of [](ClO4)2 and the meso (ΔΛ) diastereomeric form of [](ClO4)2 have been determined. The crystal structure of [](ClO4)2 also reveals the hydrogen bonding interactions between its free acidic NH protons and the oxygen atoms of the perchlorate anion in the nearby asymmetric unit. Experimental and DFT/TD-DFT calculations have divulged the non-innocent feature of the doubly deprotonated L(2-) in (3+) and (3+), leading to the resonating formulation of {Os(II)(μ-L(2-))Os(III)} ↔ {Os(II)(μ-L˙(-))Os(II)}, instead of a simple mixed valent situation {Os(II)(μ-L(2-))Os(III)}. The dinuclear complexes (3+) and (3+) display one broad and moderately intense near-IR transition near 1000 nm corresponding to a mixed Os(dπ)/L(π) → Os(dπ)/L(π*) MLLMCT (metal/ligand to ligand/metal charge transfer) transition. Different experimental studies have also established the interaction of (2+) and (2+) with the selective anions.

Eine eigentümliche Elektronenstruktur, (Mn+0.5)(μ‐L.−)(Mn+0.5), wie sie zuvor nur im Zusammenhang mit Metall‐Ligand‐Charge‐Transfer‐angeregten Zuständen diskutiert worden war, konnte strukturell und über quantenchemische Analyse der rac‐ (siehe Bild) und meso‐Isomere von [(μ‐abpy){Ru(acac)2}2] (abpy=2,2′‐Azobispyridin, acac−=Acetylacetonat) etabliert werden.

In recent years, development of lead (Pb) free perovskite solar cells (PSCs) has attracted the scientific community because of their stability in air and less toxic nature. Antimony (Sb) based perovskite like‐materials such as (CH3NH3)3Sb2I9 and (NH4)3Sb2I9 have been employed as light absorbers and showed promising features for photovoltaic applications. Herein, we have utilized (NH4)3Sb2I9 as light absorber for the construction of Pb free PSCs. Moreover, we have employed a modified two step procedure for the preparation of (NH4)3Sb2I9. The developed Pb free PSCs device (FTO/CL‐TiO2/m‐TiO2/(NH4)3Sb2I9/HTM/Au) exhibited enhanced power conversion efficiency (PCE) of 0.42 % with open circuit voltage (Voc) of 945 mV.

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