A room-temperature single-crystal X-ray structure determination of the 1 : 1 adduct of 1,10-phenanthroline ('phen') with lutetium(III) acetate (as its dihydrate) is recorded. Crystals are triclinic, <P(1)over bar>, a 12.430(8), b 10.681(4), c 8.134(8) Angstrom, alpha 74.76(6), beta 84.81(7), gamma 74.29(4)degrees, Z = 2 f.u.; conventional R on \F\ was 0.031 for N-o 3939 independent 'observed' (I > 3 sigma(I)) diffractometer reflections. The complex [(N,N'-phen)(O,O'-ac)Lu(O-ac-O')(4)Lu(O,O'-ac)(N,N'-phen)].2H(2)O is binuclear, the lutetium being eight-coordinated by bidentate phen and ac (acetate) ligands and four oxygen atoms from the bridging acetate ligands. Also recorded is the structural characterization of 1 : 1 Lu(ac)(2)Cl/tpy (tpy = 2,2':6',2 "-terpyridine) as its pentahydrate; this complex is triclinic, <P(1)over bar>, a 12.410(3), b 11.559(4), c 9.976(4) Angstrom, alpha 85.19(3), beta 70.30(3), gamma 65.70(2)degrees, Z = 2, R 0.049 for N-o 4717. The complex is shown to be [(tpy)(H2O)(2)Lu(O2CCH3)(2)]Cl.3H(2)O, with the lutetium nine-coordinated by tridentate tpy, a pair of bidentate acetates and two unidentate water molecules, with the chloride uncoordinated. Structural characterizations of a number of 1 : 1 adducts of variously solvated lanthanoid(III) trichloroacetates, Ln(tca)(3), with tpy are also recorded. Yb(tca)(3)/tpy/MeOH (1 : 1 : 1) is triclinic, <P(1)over bar>, a 14.016(4), b 12.951(5), c 9.604(3) Angstrom, alpha 73.89(3), beta 76.56(3), gamma 69.20(3)degrees, Z = 2 f.u., R 0.057 for N-o 4465. The complex is mononuclear, the eight-coordinate N3YbO5 array containing tridentate tpy, unidentate methanol, and two unidentate and one bidentate chelating anions. 1 : 1 : 1 Ln(tca)(3)/tpy/OH2 adducts for Ln = La(-)Nd are triclinic, <P(1)over bar>, a approximate to 13.4, b approximate to 12.47, c approximate to 11.5 Angstrom, alpha approximate to 114.5, beta approximate to 89.9, gamma approximate to 115.6 degrees, Z = 1 binuclear array, R 0.061, 0.071 for N-o 3240, 2394. The two Ln atoms are O,O'-bridged by a pair of anions, the N(3)LnO(6) nine-coordinate lanthanoid environment being completed by a tridentate tpy, one water, one unidentate and one bidentate anion. A 1 : 1 : 1 Lu(tca)3/tpy/OH2 array, by contrast, is triclinic, <P(1)over bar>, a 16.569(8), b 14.815(5), c 14.375(6) Angstrom, alpha 62.05(3), beta 81.35(4), gamma 77.97(3)degrees, Z = 4 'mononuclear' f.u., R 0.067 for N-o 6710. The array, remarkably, contains species of both of the above types in a 1 : 2 binuclear-to-mononuclear ratio, but with water replacing methanol in the mononuclear array.