Abstract: The present invention relates to a molecular spacer arm, to a process for attachment of a molecular unit to a solid support, and also to the use of this spacer arm on analytical chips comprising molecules or biomolecules. The spacer arm has the formula (I): in which X0, X4=C, O, S, Se, N, P, As; X1-3=C, O, N, S, Se, P, As, or C1-6 aryl or heteroaryl; Z1-2=C—R, Si—R, N, P and As, where R=C1-6 alkyl; R1-3=H, or C1-6 alkyl, aryl or heteroaryl; [Gp]=protective group for >N; n, m and p=integers?1; [Sup]=H or a silanized solid support; and [mo]=H or a molecular unit intended to be covalently attached to said silanized solid support by means of said spacer arm.