Effects of the Ligand Structures on the Photoelectric Activities, a Model Study Based on Titanium–Oxo Clusters Anchored with S-Heterocyclic Ligands

Abstract

Titanium oxo clusters (TOCs) have become one of the worldwide hot research topics because they are excellent molecular TiO materials having unique photoactive properties and can been used as models of dye-sensitized solar cells (DSSCs). S-Heterocyclic ligands such as thiophene (Th) and tetrathiafulvalene (TTF) derivatives have been widely used in electronic or photoelectronic devices and solar cells. However, a study of the synthesis and properties of TOCs anchored with Th and TTF derivatives is missing. Herein four such TOCs as single crystals were synthesized and structurally c h a r a c t e r i z e d :(3), and [Ti 6 O 4 (O i Pr) 10 (L TTF ) 2 (O 3 PPh) 2 ] (4). Charge transfer from the Th or TTF electron donor to the TOC core was evaluated by electronic spectra and theoretical calculations. This work first systematically investigated the photoelectrochemistry of TOCs with different conjugated S-heterocyclic ligands in molecular levels. The photocurrent densities of these clustermodified TiO 2 electrodes were examined using DSSCs, which were well responsive to irradiation. The photocurrents of TTF cluster-modified electrodes are higher than those of the Th cluster-modified electrodes because of the sulfur-rich conjugated system.

Titanium‐Oxo Clusters with Bi‐ and Tridentate Organic Ligands: Gradual Evolution of the Structures from Small to Big

“… R′′=H: R’=C 5 H 4 N, [125] ferrocenyl [140] R′′=Et: R’=Me, [132] CMe=CH 2 [133] R′′=CH=CH 2 , CH 2 CH=CH 2 : R’=Me, [132] CMe=CH 2 [133] R′′=CH 2 ‐naphthyl, CH 2 CH 2 CH 2 Cl, [132] dodecyl: [142] R’=Me R′′=CH 2 CH 2 CH 2 Br, CH 2 CH 2 CN, CH 2 C(O)Me, CH 2 CH 2 OC(O)C(Me)=CH 2 ): R’=CMe=CH 2 [133] R′′=CH 2 Ph: R’=ferrocenyl, [141] CMe=CH 2 [133] R′′=Ph: R’=Me, [143,144] Et, CH 2 Br, CH 2 CN 4 , CH 2 CF 3 , Ph, C 6 H 4 Br, C 6 H 4 Me, C 6 H 4 NO 2 , C 6 F 5 , naphthyl, [144] CMe=CH 2 , [133] O 2 C−C 6 H 4 −COO i Pr, ferrocenyl, [141] C 6 H 4 NMe 2 , C 6 H 4 CN, [145] C 5 H 4 N, [144,146] C 5 H 3 N−NH 2 , [146] C 5 H 3 N−Cl, [139] C 6 H 4 NH 2 , C 6 H 3 (NH 2 ) 2 , C 6 H 4 N=CH−C 6 H 4 NR 2 , C 6 H 3 (N=CH−C 6 H 4 NR 2 ) 2 (R=Et, Ph), [147] C 6 H 4 C(CN)=CH−C 6 H 4 NR 2 (R=Et, Ph), CH 2 CN, [20] dimethylthio‐tetrathiafulvalenyl, 3‐thienyl [19] …”

“…R′′=Ph: R’=Me, [143,144] Et, CH 2 Br, CH 2 CN 4 , CH 2 CF 3 , Ph, C 6 H 4 Br, C 6 H 4 Me, C 6 H 4 NO 2 , C 6 F 5 , naphthyl, [144] CMe=CH 2 , [133] O 2 C−C 6 H 4 −COO i Pr, ferrocenyl, [141] C 6 H 4 NMe 2 , C 6 H 4 CN, [145] C 5 H 4 N, [144,146] C 5 H 3 N−NH 2 , [146] C 5 H 3 N−Cl, [139] C 6 H 4 NH 2 , C 6 H 3 (NH 2 ) 2 , C 6 H 4 N=CH−C 6 H 4 NR 2 , C 6 H 3 (N=CH−C 6 H 4 NR 2 ) 2 (R=Et, Ph), [147] C 6 H 4 C(CN)=CH−C 6 H 4 NR 2 (R=Et, Ph), CH 2 CN, [20] dimethylthio‐tetrathiafulvalenyl, 3‐thienyl [19] …”

“…This cluster type is more often observed, viz. for Ti 3 O(OCH 2 t Bu) 8 (O 2 CR’) 2 (R’=H, CH 2 t Bu [14] ) and Ti 3 O(O i Pr) 8 (O 2 CR’) 2 (R’=CPh 3 , [17] Ph, [16] p ‐C 6 H 4 Cl, m ‐C 6 H 4 NO 2 , [18] 3‐thienyl [19] ).…”

Metal–Organic Frameworks Based on Group 3 and 4 Metals

“…Note that only representative MOFs based on group 3 and 4 metals (excluding Sc and Hf) since 2018 and previous MOF milestones are listed; b) Linkers are abbreviated as: ABTC = 3,3′,5,5′-azobenzene-tetracarboxylate; AZDC = azobenzene-3,3′-dicarboxylate; ATDB = 4,4′-(4-amino-4H-1,2,4-triazole-3,5-diyl)-dibenzoate; ATPC = 4′,4′′,4′′′,4′′′′-(anthracene-9,10-diylidenebis(methan-1,1-diyl-1-ylidene))tetrabiphenyl-4-carboxylate; ATBC = 4,4′,4′′,4′′′-(anthracene-9,10-diylidenebis(methan-1,1-diyl-1-ylidene)) tetrabenzoate; BDC = terephthalate; BTTC = benzotristhiophene carboxylate; BHPB = hexakis(4-(4-carboxyphenyl)phenyl)benzoate; BDHA = benzene-1,4-dihydroxamic acid; BDB = 4,4′-(benzene-1,3-diyl)dibenzoate; BTDB = 4,4′-(benzo[c] [1,2,5]thiadiazole-4,7-diyl)dibenzoate; BTBA = 4,4′,4′′-(1H-benzo-[d]imidazole-2,4,7-triyl)tribenzoate; BPDC = biphenyl-4,4′-dicarboxylate; BPyDC = 2,2′-bipyridyl-5,5′-dicarboxylate; BTB = 1,3,5-benzenetrisbenzoate; CPTPY = 4′-(4-carboxyphenyl)-terpyridine; BTB = benzene tribenzoate; CBTB = 4,4′,4′′,4′′′-(9H-carbazole-1,3,6,8-tetrayl)tetrabenzoate; DCDPS = 4,4′-dicarboxydiphenyl sulfone; DTPP = 5,15-di(3,4,5-trihydroxyphenyl)porphyrin; DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid; EDDB = 4,4′-(ethyne-1,2-diyl)dibenzoate; FUM = fumarate; 2,6-NDC = naphthalene-2,6-dicarboxylate; HBCPB = 1,2,3,4,5,6-hexakis[3,5-bis(4-carboxyphenyl)phenoxymethyl]benzene; HCHC = hexakis(4-carboxyphenyl)hexabenzocoronene; H 6 CPB/HCBB = 1′,2′,3′,4′,5′,6′-hexakis(4carboxyphenyl)benzene; H 6 TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid; H 2 DHBQ = 2,5-dihydroxybenzoquinone; INA = isonicotinate; L-AA = L-Aspartic acid; MDIP = 3,3′,5,5′-tetracarboxydiphenylmethane; PDC = 2,5-pyridinedicarboxylate; P-2COOH = N,N′-di-(4-benzoic acid)-1,2,6,7-tetrachloroperylene-3,4,9,10-tetracarboxylic acid diimide; TCPP = meso-tetrakis(4-carboxylatephenyl)porphyrin; TTFTB = tetrathiafulvalene-tetrabenzoate; TDHT = 2,4,6-tri(3,4-dihydroxyphenyl)-1,3,5triazine; TCPC = 5,10,15-tris(p-carboxylphenyl)corrole; TBAPY = 1,3,6,8-tetrakis(p-benzoic acid)pyrene; TTFTB = tetrathiafulvalene tetrabenzoate; TPHB = 4,4′,4′′,4′′′,4′′′′,4′′′′-(triphenylene-2,3,6,7,10,11-hexayl)hexabenzoate; THPP = 5,10,15,20-tetrakis(3,4,5-trihydroxyphenyl)porphyrin); THBPP = 5,10,15,20-tetrakis(3,4,5-trihydroxybiphenyl)porphyrin; TPDC = 2′,5′-dimethyl-terphenyl-4,4′′-dicarboxylate; TTDA = 5′-(1H-tetrazol-5-yl)-1,1′:3′,1′′-terphenyl-4,4′′-dicarboxylate; TBCPB = 1,2,4,5-tetrakis [ Ti-oxo clusters are widely considered as a TiO 2 nanomaterial at a molecular level, and receive considerable attention due to their structural diversity as well as potential applications in catalysis, biomedicine and environments. [48] The number of Ti atoms in Ti-oxo clusters ranges from 3 to 32, including Ti 3 , [49][50][51][52] Ti 4 , [50,[52][53][54][55][56][57] Ti 5 , [57] Ti 6 ,…”

“…Ti–oxo clusters are widely considered as a TiO 2 nanomaterial at a molecular level, and receive considerable attention due to their structural diversity as well as potential applications in catalysis, biomedicine and environments. [ 48 ] The number of Ti atoms in Ti–oxo clusters ranges from 3 to 32, including Ti 3 , [ 49–52 ] Ti 4 , [ 50,52–57 ] Ti 5 , [ 57 ] Ti 6 , [ 51,52,54,55,57–64 ] Ti 7 , [ 57 ] Ti 8 , [ 54,64,65 ] Ti 9 , [ 51,55,63 ] Ti 10 , [ 66 ] Ti 11 , [ 54–56,63 ] Ti 12 , [ 57,62,66,67 ] Ti 14 , [ 50,56 ] Ti 16 , [ 54,55,61,66 ] Ti 18 , [ 51,57 ] Ti 19 , [ 63 ] Ti 20 , [ 66,68 ] and Ti 32 clusters. [ 69 ] In general, during the assembly of Ti–oxo clusters, it is vital to control the competition between acids and coordinating ligands.…”