The use of compounds of formula (1) is described, in which compounds R1, R2 and R3 are each independently of the others hydrogen; C1-C20alkyl; C3-C7cycloalkyl; C2-C20alkenyl; C4-C7cycloalkenyl; C2-C20alkynyl, C4-C7cycloalkynyl; or unsubstituted or C1-C5alkyl-, C3-C7cylcoalkyl-, C1-C5alkoxyl-, C3-C7cycloakoxy-, halo-, oxo-, carboxy-, carboxy-C1-C7alkyl ester-, carboxy-C3-C7cylcloalkyl ester-, cyano-, trifluoromethyl-, pentafluoroethyl-, amino-, N,N-mono- or di-C1-C20alkylamino- or nitro-substituted phenyl-C1-C5alkyl, naphthyl-C1-C5alkyl, phenylcarbonyl-C1-C5alkyl, naphthylcarbonyl-C1-C5alkyl, pyrrolylalkyl, furanylalkyl, thiophenylalkyl, pyrazolylalkyl, imidazolylalkyl, oxazolylalkyl, thiazolylalkyl, isoxazolylalkyl, isothiazolylalkyl, 1,2,3-triazolylalkyl, 1,2,4-triazolylalkyl, 1,2,3-oxadiazolylalkyl, 1,3,4-oxadiazolylalkyl, 1,2,3-thiadiazolylalkyl, 1,3,4-thiadiazolylalkyl, indolylalkyl, pyridylalkyl, pyridazinylalkyl, pyrimidinylalkyl, pyridazinylalkyl, quinolinylalkyl, isoquinolinylalkyl, pyrrolyl, furanyl, thiophenyl, pyrazolyl, imidazolyl, oxazolyl, thiazolyl, isoxazolyl, isothiazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, 1,2,3-oxadiazolyl, 1,3,4-oxadiazolyl, 1,2,3-thiadiazolyl, 1,3,4-thiadiazolyl, indolyl, pyridyl, pyridazinyl, pyrimidinyl, pyridazinyl, quinolinyl or isoquinolinyl; R4, R5, R6 and R7 are each independently of the others hydrogen; C1-C20alkyl; C3-C7 cycloalky; C2-C20alkenyl; C4-C7 cycloalkenyl; C2-C20alkynyl; or C4-C7 cycloalkynyl; and m and n are each independently of the other 0 or 1, for antimicrobial treatment of surfaces. The compounds exhibit a pronounced activity against pathogenic gram-positive and gram-negative bacteria, and also against yeasts and moulds. They are accordingly suitable for the antimicrobial treatment, especially preservation and disinfection, of surfaces.