One-dimensional structures of manganese(II), copper(II) and cobalt(II) coordination complexes [MnII(hfac)2L] (hfac = hexafluoroacetylacetonate anion;: L=4,4-bipyridyl), [CuII(hfac)2L] (L=1,3-dipyridylpropane or 4,4-bipyridyl-N,N′-dioxide) and [CoII(hfac)2L] (L=4,4-bipyridyl-N,N′-dioxide)