Materials Chemistry and Physics 114 (2009) 456–461 Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Spectral characterisation of five volatile bis(N-R-salicylaldimine)nickel(II) (where n-R = methyl to pentyl) complexes and single crystal study on methyl analogue S. Arockiasamy a,∗ , M.G. Johnson a , C. Mallika b , O.M. Sreedharan a , K.S. Nagaraja a,∗ a Department of Chemistry and Loyola Institute of Frontier Energy (LIFE), Loyola College, Chennai TN-600034, India b Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam TN-603102, India article info Article history: Received 15 March 2007 Received in revised form 21 September 2008 Accepted 27 September 2008 Keywords: Chemical vapour deposition Infrared spectroscopy Crystal structure Mass spectra and precursors abstract Five novel volatile complexes of nickel, namely bis(N-R-salicylaldimine)nickel(II) (where n-R=methyl to pentyl), were characterised using fast atom bombardment mass spectrometry (FABMS). The molecular masses (M) of the monomeric species [NiL 2 ] (L = N-R-salicylaldimine) were identified to be m/z (Dal- ton)=327, 355, 383, 411 and 439, respectively, for methyl to pentyl homologues in agreement with the theoretical values. The melting and sublimation/vapourisation temperatures under reduced pressure (∼2mbar) were indicative of a negative volume change upon melting for all the homologues besides confirming their volatility to nil residue in the temperature range 305–340 ◦ C. The coordination of nitro- gen (N with n-alkyl chains) to the nickel centre that is thought to be responsible for their volatility was confirmed by Fourier-transformed infrared (FT-IR) spectroscopic analysis;  (Ni N) (cm -1 ): 502 (methyl), 522 (ethyl), 533 (propyl), 531 (butyl) and 549 (pentyl). Single crystal XRD analysis of the first member of this series, namely bis(N-methyl-salicylaldimine)nickel(II), confirmed the existence of this complex to be a monomer in the solid state and the crystal data are: 293 (2) K, a = 8.352 (3) Å, b = 7.103 (2) Å, c = 12.1369 (18) Å, ˛ = 90 ◦ , ˇ = 92.850 (18) ◦ ,  = 90 ◦ , monoclinic, space group P21/a, Z = 2. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Volatile complexes of nickel could be used as the precursors for chemical vapour deposition (CVD) of thin films of metallic nickel, which find applications in various fields as addressed else- where [1–5]. Alkoxide based soluble nickel complexes could be used as potential precursors for depositing nickel based films using liquid injection CVD [6,7]. In CVD processes, the precur- sor chemistry, reagent gas concentration, possible fragmentation pattern (in the MOCVD reactors) and vapour pressures of the precursors must be considered to have control of composition and thickness as well as the desired microstructure of metal- lic or metal-oxide thin films [8–12]. Most of the requirements, for an ideal precursor [13,14], were found to be fulfilled by a homologous series of bis(N-R-salicylaldimine)nickel(II) (where n- R = methyl to pentyl) complexes whose thermogravimetry (TG) studies and equilibrium vapour pressures by a TG-based tran- ∗ Corresponding authors. Tel.: +91 44 28178200; fax: +91 44 28175566. E-mail addresses: sa samy@yahoo.com (S. Arockiasamy), ksnagi@vsnl.net (K.S. Nagaraja). spiration technique were recently reported [3] by the present authors. The validity of these measurements was required to be aug- mented by independent mass spectral studies which in turn would also throw light on the fragmentation behaviour, for a better under- standing of the CVD processes [8–12]. The congruent vapourisation of these five homologues under reduced pressure, besides being verified by mass spectral studies, would also facilitate the con- trolled gas phase transport from their feed stock chamber to the CVD reactor under vacuum for a better tuning of deposition rate. During the evolution of these volatile precursors of nickel (NiN 2 O 2 ), the coordination of N of ( C N ) instead of O of ( C O) (see Table 1 for structures) to the nickel atom was found to play a vital role in enhancing the volatility of the purely O coordinated par- ent Ni complex namely, bis(salicylaldehydato)nickel(II) dihydrate (Ni(sal) 2 (H 2 O) 2 , NiO 4 ) and the evidence for N coordination was obtained from Fourier-transformed infrared spectroscopy (FT-IR) analyses. Thus, this paper essentially presents the results of the fast atom bombardment mass spectrometry (FABMS), FT-IR and their vapour transport study under reduced pressure. The single crystal anal- ysis of a typical methyl substituted homologue is also presented 0254-0584/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2008.09.076