Three　rare-earth　complexes　with　3-methylbenzoic　acid　(HL)　have　been　hydrothermally　synthesized　directly:　Yb(C8H7O2)3　1　and　Ln(C8H7O2)3·(4,4-bipy)0.5　(Ln　=　Eu　2,　Gd　3)　(4,4-bipy　=　4,4-bipyridine).The　crystal　structures　were　determined　by　single　crystal　X-ray　diffraction　with　the　following　data:　1:　monoclinic,　P21/n,　a　=　13.574(3),　b　=　8.0438(2),　c　=　20.652(4)　Å,　β　=　96.14(3)°;　2:　triclinic,　P-1,　a　=　8.1788(2),　b　=　12.952　(3),　c　=　12.968(3)　Å,　α　=　94.400(3)°,　β　=　92.260(4),　γ　=　101.360(4);　the　complex　1　is　a　one-dimensional　chain.　However,　due　to　the　existence　of　the　second　ligand-4,4-bipy,　the　complexes　2　and　3　are　a　two-dimensional　layer,　the　Lanthanide　contraction　makes　the　difference　of　the　structure　between　the　complexes　at　the　same　time.　Additionally,　in　order　to　explore　the　structural　characteristic,　the　2D-IR　correlation　spectroscopy　containing　the　temperature-induced　structural　variations　and　magnetism-induced　structural　variations　is　used.　Photo-luminescent　properties　of　1　and　2　are　discussed　in　detail.　©　2008　Elsevier　B.V.　All　rights　reserved.