Search

Layered sandwich metallacarboranes have various advantages including structural diversity, tailoring ability, rich electrochemical properties, and high thermal stability and thus could be potential multifunctional nonlinear optical (NLO) materials. In this study, second-order NLO properties and the multi-state switching effect of the layered cobaltacarborane, induced by electrochemical behavior, were explored using density functional theory (DFT). The calculated first hyperpolarizabilities (β) illustrated that the NLO responses are enhanced with the increasing of layers, which was mainly attributed to the C → B intraligand charge transfer (C2B3) (ILCT) and metal-centered d → d transition (MCT) as indicated by the time-dependent (TD)DFT results. Remarkable β contrasts were observed after undergoing two sequential one-electron redox processes. Therefore, the pronounced multi-state NLO switch can be achieved. In mixed-valence systems, the metal–metal interaction plays a crucial role in the NLO responses thro...

N-Substituted porphyrins are well-known for the distortion they exhibit of the porphyrin plane through the sp(3) hybridization of one of the pyrrolenic units. They have served as model compounds in investigations of many biochemical processes. In this paper, we developed an efficient route to N-substituted porphyrins, and report the synthesis of a series of new N-substituted cobaltacarborane-porphyrins containing one or two cobaltabisdicarbollide anions linked by (CH(2)CH(2)O)(2) chains to either the core porphyrin nitrogens or to a meso-aminophenyl group. These conjugates show different degrees of distortion of the porphyrin macrocycle, which affect their spectroscopic and electrochemical properties. In particular, the core N-substituted conjugates show significant fluorescence quenching in comparison with the noncore substituted macrocycles. The X-ray structures of two targeted core N-cobaltacarborane porphyrin conjugates are presented. The electrochemical and spectroelectrochemical properties of these porphyrin conjugates were investigated; while the peripheral N-substituted cobaltacarboranylporphyrins undergo three reversible reductions and three reversible oxidations (two attributed to the porphyrin and one to the Co(III) cluster), the core N-substituted porphyrins exhibit complicated electrochemical behavior with coupled chemical reactions.

The introduction of organic and inorganic substituents onto η5-C5H5 (Cp) ligands in the small cobaltacarboranes CpCo(Et2C2B4H4) and nido-CpCo(Et2C2B3H5) and their derivatives has been explored, together with metal-promoted C−C coupling to generate polycluster species featuring Cp−Cp and Cp−benzene linkages. This approach supplements alternative synthetic strategies based on functionalization of boron vertexes via metal-promoted B−C coupling, as described in a series of recent papers from our group,4,5 and affords complexes of novel architecture as well as improved routes to previously known types. Among the new compounds are triple-sandwich trinuclear and hexanuclear benzene-centered complexes in which three cobaltacarborane units are anchored to a central 1,3,5-(η5-C5H4)3C6H3 hydrocarbon scaffold. The fulvalene-bridged dinuclear species [(2,3-Et2C2B4H4)Co(η5-C5H4)]2 (7) and (closo-2,3-Et2C2B4H4)(nido-2,3-Et2C2B3H5)Co2(η5-C5H4)2 (8), previously obtained by Davis et al.7 from the fulvalenide dianion, were ...

A series of ferratricarbaboranyl complexes, closo-1-(eta-C(5)H(5))FeRC(3)B(7)H(9) [R- = H-, NCCH(2)-, MeOC(O)CH(2)-], have been generated by the reactions of (eta-C(5)H(5))Fe(CO)(2)I with tricarbaboranyl arachno-6-R-5,6,7-C(3)B(7)H(11)(-) anions. Structural characterizations of closo-1-(eta-C(5)H(5))Fe-2-(NCCH(2))-2,3,4-C(3)B(7)H(9), 1c, closo-1-(eta-C(5)H(5))Fe-3-(NCCH(2))-2,3,4-C(3)B(7)H(9), 1d, closo-1-(eta-C(5)H(5))Fe-2-(MeCH(3)OC(O)CH(2))-2,3,4-C(3)B(7)H(9), 2b, and closo-1-(eta-C(5)H(5))Fe-3-(MeOC(O)CH(2))-2,3,4-C(3)B(7)H(9), 2c, show the ferratricarbaboranyl cages in these complexes have closo-octadecahedral structures containing carbon atoms in the two four-coordinate positions closest to the iron. Other isolated products arise from further reactions of the side chain groups, with crystallographically characterized products including the multicage complex (m(2,12)(')-CH(2))[closo-1-(eta-C(5)H(5))Fe-2,3,4-C(3)B(7)H(9)][arachno-5'-(NCCH(2))-5',7',9',12',11'-C(4)NB(7)H(10)], 1e, and the first polyboron metallapentacarbaborane nido-2-(eta-C(5)H(5))Fe-7-Me-7,8,9,10,12-C(5)B(6)H(10), 3c. Cobaltatricarbaboranes of general formula 1-(eta-C(5)H(5))Co(NCCH(2))C(3)B(7)H(9), 4b-d, along with the unique multimetal cluster commo-Co-[closo-1-Co-8,9-((eta-C(5)H(5))Co)(2)-2,3,5-C(3)B(7)H(10)][closo-2'-Co-3'-(NCCH(2)CH(2))-1',10'-C(2)B(7)H(8)], 4e, were isolated from the reaction of cobalt chloride with a mixture of the arachno-6-NCCH(2)-5,6,7-C(3)B(7)H(11)(-) and cyclopentadienyl anions.

The closo-cohaltacarboranes Cp . Co[(Me 3 Si) 2 C 2 B 4 H 4 ] (Cp . =η 5 -C 5 Me 5 ) and (η 5 -C 5 Ph 5 )Co[(Me 3 Si) 2 C 2 B 4 H 4 ] were catalytically desilylated by tetrahutylammonium fluoride in wet THF at room temperature, generating the respective (C 5 R 5 )Co(C 2 B 4 H 6 ) parent complexes (6a, R=Me; 6b, R=Ph).