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Two-electron reductions of 3,3′-bis(2,6-dimesitylpyridin-4-yl)-1,1′-biphenyl 1 with elemental potassium in the absence and presence of 18-c-6 afforded the diradical dianion salts [K+]2˙[trans-1]˙˙2− and [K(18-c-6)]+2˙[cis-1]˙˙2−, which exhibit trans and cis configurations, respectively. The transoid conformer could be converted to the cisoid one through reacting with 18-c-6. [ABSTRACT FROM AUTHOR]

The reactions of dipotassium 3,4-dimethyl-2,5-bis(trimethylsilyl)-germole dianion K2[1] with YCl3 and Cp*YCl2 (Cp* = cyclopentadienyl) in THF at room temperature afforded the dianion salt [(K-cryptand-222)2][1-YCl3] (K2[2]) and the dimeric complex [1-Y-Cp*]2 (3), respectively. While the polymeric complex {[(1)2-Y-K(toluene)]2}n (4) was obtained from the reaction of K2[1] and half molar equivalent of YCl3(THF)3.5 in toluene at 80 °C. The germole dianions in complexes 3 and 4 feature η5/η1 coordination interactions with the yttrium atoms. They represent the first examples of rare earth (RE) complexes containing RE–Ge bonds other than the RE–GeR3 structural type. [ABSTRACT FROM AUTHOR]

Although diradicals and azaacenes have been greatly attractive in fundamental chemistry and functional materials, the isolable diradical dianions of azaacenes are still unknown. Herein, we describe the first isolation of pyrene‐fused azaacene diradical dianion salts [(18‐c‐6)K(THF)2]+[(18‐c‐6)K]+⋅12−.. and [(18‐c‐6)K(THF)]2+⋅22−.. by reduction of the neutral pyrene‐fused azaacene derivatives 1 and 2 with excess potassium graphite in THF in the presence of 18‐crown‐6. Their electronic structures were investigated by various experiments, in conjunction with theoretical calculations. It was found that both dianions are open‐shell singlets in the ground state and their triplet states are thermally readily accessible owing to the small singlet–triplet energy gap. This work provides the first examples of crystalline diradical dianions of azaacenes with considerable diradical character. [ABSTRACT FROM AUTHOR]

Azo radical anion 1˙− and dianion 12− have been isolated by one- and two-electron reduction of the azo compound 1 (ArNNAr, Ar = 4-CN-2,6-iPr2-C6H2) with alkali metals, respectively. The reduced species have been characterized by single-crystal X-ray analysis, EPR, UV and FT-IR spectroscopy, as well as SQUID measurements. The filling of one and two electrons in the π* orbital of the N–N double bond of 1 leads to a half-double N–N bond in 1˙− and a single N–N bond in 12−. The uncoordinated nature of these reduced species enables them to activate CO2. The exposure of 1˙− solution to CO2 led to the formation of oxalate anion C2O42−, while that of 12− solution to CO2 afforded the hydrazine dicarboxylate dianion [1-2CO2]2−, which reversibly dissociated back to 1 and CO2 upon oxidation. [ABSTRACT FROM AUTHOR]

The reduction of 2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine (TPT) with alkali metals resulted in four radical anion salts (1, 2, 4 and 5) and one diradical dianion salt (3). Single‐crystal X‐ray diffraction and electron paramagnetic resonance (EPR) spectroscopy reveal that 1 contains the monoradical anion TPT.− stacked in one‐dimensional (1D) with K+(18c6) and 2 can be viewed as a 1D magnetic chain of TPT.−, while 4 and 5 form radical metal‐organic frameworks (RMOFs). 1D pore passages, with a diameter of 6.0 Å, containing solvent molecules were observed in 5. Variable‐temperature EPR measurements show that 3 has an open‐shell singlet ground state that can be excited to a triplet state, consistent with theoretical calculation. The work suggests that the direct reduction approach could lead to the formation of RMOFs. [ABSTRACT FROM AUTHOR]

Selective reduction of 1,5-diazacyclooctatetraenes with potassium or a Co(i) complex was achieved to provide the first structurally well-defined aromatic 1,5-diazacyclooctatetraenyl dianion or a novel dinuclear Co(ii) complex bridged by a bipyrrolinyl dianion, respectively. [ABSTRACT FROM AUTHOR]

Abstract: One‐electron reductions of Mes*As=Fl* (1; Fl*=2,7‐di‐tert‐butylfluorenylidene, Mes*=2,4,6‐tBu3C6H2) and diarsaalkenes [1,2‐b]‐IF(=AsMes*)2 (2; IF=indenofluorene) with potassium led to the isolation of the arsenic‐centered radical anion salts 1K and 2K, respectively. The diradical dianion salts 2K2 and 3K2 were afforded by the reduction of 2 and 2,8‐tBu2‐[2,1‐b]‐IF(=AsMes*)2 (3) with an excess amount of KC8. The radicals have been investigated by single‐crystal X‐ray crystallography, EPR, and UV/Vis absorption spectroscopy, along with theoretical calculations. The calculations revealed that 2K2 and 3K2 feature open‐shell singlet ground states with singlet‐triplet energy gaps of 2.1 and 1.0 kcal mol−1, respectively. They are readily thermally excited to triplet states as demonstrated by EPR spectroscopy. The obtained diradicals represent the first examples of heavier Group 15 element centered diradicals with experimentally observable triplet states. [ABSTRACT FROM AUTHOR]