Seven 5-benzylamino-3-tert-butyl-1-phenyl-1H-pyrazoles: unexpected isomorphisms, and hydrogen-bonded supramolecular structures in zero, one and two dimensions.

5-Benzylamino-3-tert-butyl-1-phenyl-1H-pyrazole, C(20)H(23)N(3), (I), and its 5-[4-(trifluoromethyl)benzyl]-, C(21)H(22)F(3)N(3), (III), and 5-(4-bromobenzyl)-, C(20)H(22)BrN(3), (V), analogues, are isomorphous in the space group C2/c, but not strictly isostructural; molecules of (I) form hydrogen-bonded chains, while those of (III) and (V) form hydrogen-bonded sheets, albeit with slightly different architectures. Molecules of 3-tert-butyl-5-(4-methylbenzylamino)-1-phenyl-1H-pyrazole, C(21)H(25)N(3), (II), are linked into hydrogen-bonded dimers by a combination of N-H...pi(arene) and C-H...pi(arene) hydrogen bonds, while those of 3-tert-butyl-5-(4-chlorobenzylamino)-1-phenyl-1H-pyrazole, C(20)H(22)ClN(3), (IV), form hydrogen-bonded chains of rings which are themselves linked into sheets by an aromatic pi-pi stacking interaction. Simple hydrogen-bonded chains built from a single N-H...O hydrogen bond are formed in 3-tert-butyl-5-(4-nitrobenzylamino)-1-phenyl-1H-pyrazole, C(20)H(22)N(4)O(2), (VI), while in 3-tert-butyl-5-(3,4,5-trimethoxybenzylamino)-1-phenyl-1H-pyrazole, C(23)H(29)N(3)O(3), (VII), which crystallizes with Z' = 2 in the space group P-1, pairs of molecules are linked into two independent centrosymmetric dimers, one generated by a three-centre N-H...(O)(2) hydrogen bond and the other by a two-centre N-H...O hydrogen bond.