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Tunable Supramolecular Synthons and Versatile, Water‐Soluble Building Blocks for Crystal Engineering: [(η 5 ‐C 5 H 4 COOH) 2 Co III ] + and its Zwitterionic Form [(η 5 ‐C 5 H 4 COOH)(η 5 ‐C 5 H 4 COO)Co III ]
Author(s) -
Braga Dario,
Maini Lucia,
Polito Marco,
Rossini Michele,
Grepioni Fabrizia
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20001117)6:22<4227::aid-chem4227>3.0.co;2-z
Subject(s) - zwitterion , deprotonation , supramolecular chemistry , hydrogen bond , chemistry , synthon , protonation , cationic polymerization , crystallography , ether , crystal engineering , salt (chemistry) , methanesulfonic acid , crystal structure , inorganic chemistry , medicinal chemistry , stereochemistry , polymer chemistry , molecule , organic chemistry , ion
It is shown that the water‐soluble dicarboxylic cationic acid [(η 5 ‐C 5 H 4 COOH) 2 Co III ] + ( 1 ) is an extremely versatile building block for the construction of organometallic crystalline edifices. Removal of one proton from 1 leads to formation of the neutral zwitterion [(η 5 ‐C 5 H 4 COOH)(η 5 ‐C 5 H 4 COO)Co III ] ( 2 ), while further deprotonation leads to formation of the dicarboxylate monoanion [(η 5 ‐C 5 H 4 COO) 2 Co III ] − ( 3 ). Compounds 1, 2 and 3 possess different hydrogen‐bonding capacity and participate in a variety of hydrogen‐bonding networks. The cationic form 1 has been characterised as its [PF 6 ] − and Cl − salts 1 ‐[PF 6 ] and 1 ‐Cl⋅H 2 O, as well as in its co‐crystal with urea, 1 ‐Cl⋅3 (NH 2 ) 2 CO, and with the zwitterionic form 2 , [(η 5 ‐C 5 H 4 COOH)(η 5 ‐C 5 H 4 COO)Co III ][(η 5 ‐C 5 H 4 COOH) 2 Co III ] + [PF 6 ] − , 2 ⋅ 1 ‐[PF 6 ]. The neutral zwitterion 2 behaves as a supramolecular crown ether: it encapsulates the alkali cations K + , Rb + and Cs + as well as the ammonium cation NH 4 + in cages sustained by O−H⋅⋅⋅O and C−H⋅⋅⋅O hydrogen bonds to form co‐crystalline salts of the type 2 2 ‐M[PF 6 ] (M=K, Rb, Cs) and 2 2 ‐[NH 4 ][PF 6 ]. The deprotonated acid 3 has been characterised as its Cs + salt, Cs + ‐ 3 ⋅3 H 2 O.