Secondary Donor Research Articles

Structure and properties of silver sulfate complexes derived from dipyridyl methylthio ligands with secondary donor site

Dipyridyl sulphide ligands 4-(pyridin-4-ylmethylthio)pyridine (abbreviated as L1) and 3-(pyridin-4-ylmethylthio)pyridine (abbreviated as L2) have been designed and used as μ-N,N-bridging linkages to construct coordination polymers with free –S–CH2– groups as secondary donor sites. By use solvent control method, coordination polymers {[Ag3SO4(L1)3](Cl)·4.5H2O}∞(1), {[Ag2SO4(L1)2]·6H2O·2CH3OH}∞(2), {[Ag2SO4(L2)2]·H2O}∞(3) and {[Ag4(SO4)2(L2)4]·5H2O}∞(4) with different architectures were obtained. Complexes 1, 3 and 4 feature 1D channel with different sizes and structures. Complex 1 exhibits guest exchange by THF and 1,4-dioxane, and Hg2+ sorption ability from solution due to its relative larger channel and available bonding sites of –S– exposed to the channel region. All complexes have been characterized through single-crystal and powder X-ray diffraction (PXRD), FT-IR spectra, X-ray photoelectron spectroscopy (XPS), elemental and thermogravimetric analyses. The guest exchange and Hg2+ sorption were monitored and identified, and the structure-property relationship of coordination polymers 1–4 are discussed.

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension.

The synthesis of key 4-alkyl-substituted 5-(trimethylsilyl)thiophene-2-boronic acid pinacol esters 3 allowed a simplified alkylthiophene catenation process to access bis-, ter-, quater-, and quinquethiophene π-bridges for the synthesis of acceptor–π-bridge-donor– π-bridge-acceptor (A–π-D–π-A) electron donor molecules. Based on the known benzodithiophene-terthiophene-rhodanine (BTR) material, the BXR series of materials, BMR (X = M, monothiophene), BBR (X = B, bithiophene), known BTR (X = T, terthiophene), BQR (X = Q, quaterthiophene), and BPR (X = P(penta), quinquethiophene) were synthesised to examine the influence of chromophore extension on the device performance and stability for OPV applications. The BTxR (x = 4, butyl, and x = 8, octyl) series of materials were synthesised by varying the oligothiophene π-bridge alkyl substituent to examine structure–property relationships in OPV device performance. The devices assembled using electron donors with an extended chromophore (BQR and BPR) are shown to be more thermally stable than the BTR containing devices, with un-optimized efficiencies up to 9.0% PCE. BQR has been incorporated as a secondary donor in ternary blend devices with PTB7-Th resulting in high-performance OPV devices with up to 10.7% PCE.

Electronic properties of Si-doped AlxGa1−xN with aluminum mole fractions above 80%

The dependence of the activation energy as well as the energetic levels of the neutral charge state and the DX center of the Si donor in AlxGa1−xN:Si samples on aluminum content and SiH4/III ratio were investigated by electron paramagnetic resonance (EPR) measurements, Van-der-Pauw resistivity measurements, and Hall-effect measurements. It was found by EPR measurements that the energy distance of the neutral charge state of the Si donor from the conduction band increases with increasing aluminum content from 61 meV for x = 0.82 to 106 meV for x = 0.89. Additionally, the formation of a DX center below the neutral charge state which is deepening from 6 meV for x = 0.82 to 58 meV for x = 0.89 is observed. This results in a linearly increasing activation energy with increasing aluminum content from 67 meV for x = 0.82 to 164 meV for x = 0.89. This is consistent with the activation energies as determined by Hall-effect measurements showing a linear increase from 24 meV for x = 0.85 to 211 meV for x = 0.96, as well as the activation energies as determined by Van-der-Pauw resistivity measurements. By varying the SiH4/III ratio we observed a formation of a minimum resistivity in accordance with the room temperature charge carrier density. However, no clear dependence of the activation energy was observed. EPR measurements of samples with a high SiH4/III ratio hint to an increased incorporation probability of a deep secondary donor species which might explain the increase in resistivity.

Versatility and “flap efficiency” of pedicled perforator flaps in lower extremity reconstruction

The use of pedicled perforator flaps provides an alternative to free tissue transfer for lower limb reconstruction. We use computer-aided image analysis to investigate the versatility of pedicled perforator flaps for the reconstruction of lower limb defects. Between April 2007 and April 2011, a case series of 61 patients with wounds of the lower extremity from knee to ankle were reconstructed with pedicled perforator flaps. We performed 16 pedicled reverse-flow anterolateral thigh (RF-ALT) flaps, 8pedicled medial sural artery perforator (MSAP) flaps, 26 pedicled peroneal artery perforator (PAP) flaps, and 11 pedicled posterior tibial artery perforator (PTAP) flaps. Digital planimetry of defects covered was analyzed and the "efficiency" of each flap was calculated, which allowed the assessment of the merits of each flap in the management of lower limb defects. Flaps healed primarily in 82% of cases (50/61). Approximately 50% of the secondary donor sites required skin grafting. Complications requiring secondary surgery occurred in 18% (11/61) of the cases. Six required secondary skin grafting (10%). One RF-ALT flap was converted into a free flap, one PAP required arterial supercharging, and three pedicled RF-ALT flaps required venous supercharging. Image analysis showed that these pedicled perforator flaps could cover 75% of the surface area of the lower leg. The higher length of perforator allowed for greater "flap efficiency" and better versatility of tissue cover. Image analysis can be used as a modality to assess the versatility of individual flaps in the reconstruction of lower limb defects.

Buttock Reconstruction in Sarcoma Surgery: An Esthetic Sigmoidplasty Closure for Large Circular Defects Using Double Opposing Skin Flaps.

Background:Large defects arising from extirpation surgery of buttock sarcomas requiring adjuvant radiotherapy are best closed with flap surgery. The traditional solutions are derived from an approach to pressure sores, which were designed for the ischial, sacral, or trochanteric areas, and have now been adapted for true buttock defects. This invariably destroys the esthetics of the buttock. We describe a novel technique of sigmoidplasty, which preserves most of the esthetic features.Methods:We report on a retrospective review of 11 consecutive buttock sarcomas managed at our institution between 2009 and 2014, focusing on those for which the described reconstruction method was used (N = 5).Results:The immediate outcome was very good. In 1 patient, partial loss of 1 of the flaps and the management thereof resulted in a minor contour deformity. In general, the buttock volume was significantly decreased but the shape was preserved. This was obtained without secondary donor defect and with minimal contour irregularity. Long-term follow-up remained pleasing, and all patients were satisfied with the outcomes.Conclusions:The described technique of buttock defect closure satisfies the oncoplastic principles of tumor surgery with the added benefit of superior esthetics. We suggest that it is a versatile adjunct to the reconstructive surgeon’s armamentarium for buttock reconstruction after sarcoma excision, particularly when the gluteal artery perforator systems are unavailable.

The Role of Nitrogen Donors in Zinc Catalysts for Lactide Ring-Opening Polymerization.

The electronic effects of nitrogen donors in zinc catalysts for ring-opening polymerization of cyclic esters were investigated. Alkyl and benzyloxy zinc complexes supported by tridentate diamino- and aminoimino phenolate ligands were synthesized, and their solid-state and solution structures characterized. The solution-state structures showed that the alkyl complexes are mononuclear, while the alkoxy complexes are dimeric with the ligands coordinated with different denticities depending on the nature of the ligand donors. The catalytic activities of these compounds toward the ring-opening polymerization of racemic lactide were studied and showed that catalysts with secondary and imine nitrogen donors are more active than analogues with tertiary amines.

Globin domain interactions control heme pocket conformation and oligomerization of globin coupled sensors

Globin coupled sensors (GCS) are O2-sensing proteins used by bacteria to monitor the surrounding gaseous environment. To investigate the biphasic O2 dissociation kinetics observed for full-length GCS proteins, isolated globin domains from Pectobacterium carotovorum ssp. carotovorum (PccGlobin), and Bordetella pertussis (BpeGlobin), have been characterized. PccGlobin is found to be dimeric, while BpeGlobin is monomeric, indicating key differences in the globin domain dimer interface. Through characterization of wild type globin domains and globin variants with mutations at the dimer interface and within the distal pocket, dimerization of the globin domain is demonstrated to correlate with biphasic dissociation kinetics. Furthermore, a distal pocket tyrosine is identified as the primary hydrogen bond donor, while a secondary hydrogen bond donor within the distal heme pocket is involved in conformation(s) that lead to the second O2 dissociation rate. These findings highlight the role of the globin dimer interface in controlling properties of both the heme pocket and full-length GCS proteins.

Nasal radix augmentation in rhinoplasty: suggestion of an algorithm

The purpose of this study was to evaluate four standard techniques for radix augmentation during primary rhinoplasty: Skoog, crushed septal cartilage, temporalis fascia, and crushed cartilage wrapped in temporalis fascia. The main criterion for a patient to be included in this study was the need for radix augmentation, which was determined through preoperative evaluations. All patients requiring total dorsal augmentation were excluded from the study. This study included 63 rhinoplasty patients who underwent radix augmentation. The Skoog technique was applied in 15 patients, crushed septal cartilage in 16, temporalis fascia in 17, and crushed cartilage wrapped in temporalis fascia in 15. In those undergoing the Skoog technique, sharp edges of graft were palpable in three patients and were even visible in one patient. In the crushed cartilage group, seven patients showed irregularities during the postoperative follow-up. The results of this study indicate that all four autologous grafts represent acceptable graft material for radix augmentation. The algorithm suggests using the easier techniques first and that secondary donor sites should be considered only when the ideal result is not achieved.

Indolo[3,2-b]carbazole-based multi-donor–π–acceptor type organic dyes for highly efficient dye-sensitized solar cells

Four novel indolo[3,2-b]carbazole-based multi-donor–π–acceptor type organic dyes QX01–04 have been designed, synthesized, and applied for dye-sensitized solar cells. These dyes consist of an indolo[3,2-b]carbazole core acting as the main donor group, a couple of groups such as ethylbenzene, N,N-diethylaniline, ethyloxylbenzene, and octyloxylbenzene acting as the secondary donors. The photophysical, electrochemical, and theoretical studies indicate that the four dyes are all capable as the photosensitizers. When introducing N,N-diethylaniline as the secondary donor, QX02 exhibits a broader absorption region and significantly improved IPCE values, which ensured a good light-harvesting ability and a high Jsc of 15.2 mA cm−2. Finally, QX02-based cell achieved a high efficiency of 8.09% which is very close to that of the commercial N719-based cell (8.26%) under 100 mW cm−2 irradiation.

Effect of Spacer Connecting the Secondary Electron Donor Phenothiazine in Subphthalocyanine-Fullerene Conjugates in Promoting Electron Transfer Followed by Hole Shift Process.

Sequential electron/hole transfer between energetically well-positioned entities of photosynthetic reaction center models is one of the commonly employed mechanisms to generate long-lived charge-separated states. A wealth of information, applicable towards light energy harvesting and building optoelectronic devices, has been acquired from such studies. In the present study, we report on the effect of spacer (direct or via phenoxy linkage) connecting the hole shifting agent, phenothiazine (PTZ), on photoinduced charge stabilization in subphthalocyanine-fullerene donor-acceptor conjugates. In these conjugates, the subphthalocyanine (SubPc) and fullerene (C60 ) served as primary electron donor and acceptor, respectively, while the phenothiazine entities act as hole shifting agents. The newly synthesized compounds were characterized by optical absorption and emission, computational, and electrochemical methods. The redox potentials measured using differential pulse voltammetry were used to estimate free-energy changes for charge separation, hole migration, and charge recombination processes. Using femto- and nanosecond transient absorption techniques, evidence for charge separation, and kinetics of charge separation and recombination were obtained in polar benzonitrile and nonpolar toluene solvents. In the conjugate where the phenothiazine entities are directly linked to SubPc, evidence for sequential electron transfer followed by hole shift leading to long-lived charge separated state was weak, primarily due to the delocalization of HOMO on both SubPc and PTZ entities. However, in case of the conjugate where the PTZ and SubPc are linked via phenoxy spacers, sequential electron transfer/hole shift was observed leading to the formation of long-lived charge-separated states. The present study brings out the importance of the spacer group connecting the hole shifting agent in model donor-acceptor conjugates to generate long-lived charge-separated states.

Harvests from bone marrow donors who weigh less than their recipients are associated with a significantly increased probability of a suboptimal harvest yield.

Previous studies have demonstrated the importance of bone marrow (BM) harvest yield in determining transplant outcomes, but little is known regarding donor and procedure variables associated with achievement of an optimal yield. We hypothesized that donor demographics and variables relating to the procedure were likely to impact the yield (total nucleated cells [TNCs]/kg recipient weight) and quality (TNCs/mL) of the harvest. To test our hypothesis, BM harvests of 110 consecutive unrelated donors were evaluated. The relationship between donor or procedure characteristics and the BM harvest yield was examined. The relationship between donor and recipient weight significantly influenced the harvest yield; only 14% of BM harvests from donors who weighed less than their recipient achieved a TNC count of more than 4 × 10(8) /kg compared to 56% of harvests from donors heavier than their recipient (p = 0.001). Higher-volume harvests were significantly less likely to achieve an optimal yield than lower-volume harvests (32% vs. 78%; p = 0.007), and higher-volume harvests contained significantly fewer TNCs/mL, indicating peripheral blood contamination. BM harvest quality also varied significantly between collection centers adding to recent concerns regarding maintenance of BM harvest expertise within the transplant community. Since the relationship between donor and recipient weight has a critical influence yield, we recommend prioritizing this secondary donor characteristic when selecting from multiple well-matched donors. Given the declining number of requests for BM harvests, it is crucial that systems are developed to train operators and ensure expertise in this procedure is retained.

Oligothiophene-linked D–π–A type phenothiazine dyes for dye-sensitized solar cells

Three novel phenothiazine dyes (JY31–33) featured oligothiophene π-bridge have been designed, synthesized and applied as photosensitizers for highly efficient dye-sensitized solar cells (DSSCs). The introduction of alkyl chains on oligothiophene π-bridge is found to significantly improve the open-circuit voltage of the resultant device. Phenothiazine bearing a 4-butoxyphenyl group as the secondary donor exhibits a stronger electron-donating ability and a positive acceleration on the short-circuit current density and open-circuit voltage. The dye JY33 containing a secondary donor and two alkyl chains finally gives a high efficiency of 7.48% under the 100 mW cm−2 simulated AM1.5 sunlight, with a short-circuit photocurrent density (Jsc) of 17.18 mA cm−2, an open-circuit photovoltage (Voc) of 742 mV and a fill factor (FF) of 0.59.

Synthesis and spectroscopic studies of axially bound tetra(phenothiazinyl)/tetra(bis(4′-tert-butylbiphenyl-4-yl)aniline)-zinc(II)porphyrin-fullero[C60 & C70]pyrrolidine donor–acceptor triads

Two zinc porphyrin based dyads, 5, 10, 15, 20-tetra-4-(2-(10H-phenothiazin-10-yl)ethoxy)phenyl porphyrinato zinc (II) and 5,10,15,20-tetra-4-(bis(4′-tert-butylbiphenyl-4-yl)amino)phenyl porphyrinato zinc(II) containing four phenothiazine or bis(4′-tert-butylbiphenyl-4-yl)aniline moieties tethered to porphyrin framework were synthesized, and systematically characterized using 1H NMR, mass, UV–visible and steady state fluorescence techniques. Excitation of 5,10,15,20-tetra-4-(bis(4′-tert-butylbiphenyl-4-yl)amino)phenyl porphyrinato zinc(II) at 335nm, resulted in quenched emission of bis(4′-tert-butylbiphenyl-4-yl)aniline moiety, when compared to pristine bis(4′-tert-butylbiphenyl-4-yl)aniline, and appearance of porphyrin emission at 618nm, due to intramolecular energy transfer from bis(4′-tert-butylbiphenyl-4-yl)aniline moiety to porphyrin. The porphyrin dyads were titrated with phenylimidazole appended fullerenes, N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C60]pyrrolidine or N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C70]pyrrolidine and supramolecular triads of the type, (PTZ or BBA)4-ZnP:(C60Im or C70Im) were formed in which, zinc porphyrin and fullerenes act as primary electron donor and acceptors, while phenothiazine or bis(4′-tert-butylbiphenyl-4-yl)aniline moieties behave as secondary electron donors in photo-induced electron transfer events. Optical absorption and 1H NMR titration studies confirmed the formation of supramolecular triads and the steady state fluorescence experiments revealed the quenching of porphyrin emission upon addition of increasing amounts of N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C60]pyrrolidine or N-Methyl-4-(1H-imidazol-1-yl)phenylfullero[C70]pyrrolidine indicating the occurrence of photo-induced electron transfer from 1ZnP⁎ to co-ordinated fullerene moieties.

Synthesis and Evaluation of Thiophene‐Based Organic Dyes Contain­ing a Rigid and Nonplanar Donor with Secondary Electron Donors for Use in Dye‐Sensitized Solar Cells

AbstractWe demonstrate herein the divergent synthesis of six dyes containing our originally developed rigid and nonplanar donor with three different secondary electron donors (SEDs), namely thiophene, 4‐methoxybenzene, and diphenylethene. Evaluation of the photophysical properties of the synthesized dyes revealed that the introduction of the SEDs resulted in an increased absorbance in the 350–450 nm region. The influence of the SEDs on the electrochemical and photovoltaic properties depended on their structure and position of attachment. The introduction of the thiophene SED to D4π4A2, which we previously reported to be our best dye, resulted in an increased Jsc. The dye‐sensitized solar cell (DSSC) prepared by using dye 2b, which contains the thiophene SED, shows a higher power conversion efficiency (PCE; η = 4.62 ± 0.02 %) and a higher incident photon‐to‐current conversion efficiency (IPCE) in the region 300–600 nm than D4π4A2.

Chloride-Anion-Templated Synthesis of a Strapped-Porphyrin-Containing Catenane Host System.

The synthesis, structure and anion-recognition properties of a new strapped-porphyrin-containing [2]catenane anion host system are described. The assembly of the catenane is directed by discrete chloride anion templation acting in synergy with secondary aromatic donor–acceptor and coordinative pyridine–zinc interactions. The [2]catenane incorporates a three-dimensional, hydrogen-bond-donating anion-binding pocket; solid-state structural analysis of the catenane⋅chloride complex reveals that the chloride anion is encapsulated within the catenane’s interlocked binding cavity through six convergent CH⋅⋅⋅⋅Cl and NH⋅⋅⋅Cl hydrogen-bonding interactions and solution-phase 1H NMR titration experiments demonstrate that this complementary hydrogen-bonding arrangement facilitates the selective recognition of chloride over larger halide anions in DMSO solution.

Temperature Dependence of Light-Induced Absorbance Changes Associated with Chlorophyll Photooxidation in Manganese-Depleted Core Complexes of Photosystem II.

Mid-infrared (4500-1150 cm(-1)) absorbance changes induced by continuous illumination of Mn-depleted core complexes of photosystem II (PSII) from spinach in the presence of exogenous electron acceptors (potassium ferricyanide and silicomolybdate) were studied by FTIR difference spectroscopy in the temperature range 100-265 K. The FTIR difference spectrum for photooxidation of the chlorophyll dimer P680 was determined from the set of signals associated with oxidation of secondary electron donors (β-carotene, chlorophyll) and reduction of the primary quinone QA. On the basis of analysis of the temperature dependence of the P680(+)/P680 FTIR spectrum, it was concluded that frequencies of 13(1)-keto-C=O stretching modes of neutral chlorophyll molecules PD1 and PD2, which constitute P680, are similar to each other, being located at ~1700 cm(-1). This together with considerable difference between the stretching mode frequencies of keto groups of PD1(+) and PD2(+) cations (1724 and 1709 cm(-1), respectively) is in agreement with a literature model (Okubo et al. (2007) Biochemistry, 46, 4390-4397) suggesting that the positive charge in the P680(+) dimer is mainly localized on one of the two chlorophyll molecules. A partial delocalization of the charge between the PD1 and PD2 molecules in P680(+) is supported by the presence of a characteristic electronic intervalence band at ~3000 cm(-1). It is shown that a bleaching band at 1680 cm(-1) in the P680(+)/P680 FTIR spectrum does not belong to P680. A possible origin of this band is discussed, taking into account the temperature dependence (100-265 K) of light-induced absorbance changes of PSII core complexes in the visible spectral region from 620 to 720 nm.

The combined transverse upper gracilis and profunda artery perforator (TUGPAP) flap for breast reconstruction.

Surgical options for breast reconstruction include alloplastic and autogenous reconstructions. In autologous cases where the abdomen is not a suitable primary donor site, secondary donor sites such as the thigh or buttock are considered. The aim of this report is to describe a novel approach, the combined transverse upper gracilis and profunda artery perforator (TUGPAP) flap, aimed at medium to large volume breast reconstruction, with a single donor site used per breast. Between January 2011 and June 2013, 32 consecutive unilateral immediate breast reconstruction cases were performed using free flaps. In nine cases, patients had previously undergone abdominal surgery, therefore abdominal flaps were excluded and TUGPAP flaps were performed. The TUGPAP flap consisted of the combination of two well-described flaps: the transverse upper gracilis (TUG) and the profunda artery perforator (PAP) flap. All TUGPAP flaps were based on two pedicles: the ascending branch of the medial circumflex femoral artery (MCFA) for the TUG component, and the profunda artery perforator itself for the PAP component. The mean size of the harvested skin paddle was 28.6 × 8 cm2 (range, 27 × 7 cm2 to 30 × 9 cm2). The average length of the TUG flap pedicle was 7 cm (range, 6-8 cm) and the PAP flap pedicle was 9 cm (range, 8.5-10 cm). The flap survival rate was 100% with no re-exploration, and no partial flap loss. Post-operatively there was one case of persistent donor site seroma, which was managed conservatively. With appropriate patient selection and surgical technique the TUGPAP flap could be a valuable option as an alternative method for autologous breast reconstruction. © 2015 Wiley Periodicals, Inc. Microsurgery, 2015.

ChemInform Abstract: Exploiting Metal‐Ligand Bifunctional Reactions in the Design of Iron Asymmetric Hydrogenation Catalysts

AbstractReview: 74 refs.

Novel use of the superficial inferior epigastric vein lifeboat in DIEP flap harvest

Deep inferior epigastric artery perforator (DIEP) flap reconstruction has become a well-established procedure for breast reconstruction. While vascular compromise is not common, venous congestion is the most commonly reported cause of such compromise, and of those that may require re-exploration, insufficient venous drainage is the most common cause. In such cases, flap salvage may require establishment of a secondary venous outflow source. In a standard unilateral breast reconstruction with a DIEP flap, zone IV is discarded, with the intra-flap segment of the superficial inferior epigastric vein (SIEV) unused. We describe the novel approach of harvesting the SIEV within zone IV and banking within the breast pocket near the contralateral superficial vein should it be required for further salvage surgery. Our approach involves harvest of the SIEV on a side table (which allows simultaneous operating), flushing the graft with heparinized saline, and tagging the proximal end with an 8/0 nylon suture. This vein graft is then transferred and banked at the breast recipient site, near the flap vein where it is likely to be required. This simple step prevents further morbidity of a secondary donor site and reduces operative time should re-exploration be required.

Exploiting metal-ligand bifunctional reactions in the design of iron asymmetric hydrogenation catalysts.

This is an Account of our development of iron-based catalysts for the asymmetric transfer hydrogenation (ATH) and asymmetric pressure hydrogenation (AH) of ketones and imines. These chemical processes provide enantiopure alcohols and amines for use in the pharmaceutical, agrochemical, fragrance, and other fine chemical industries. Fundamental principles of bifunctional reactivity obtained by studies of ruthenium catalysts by Noyori's group and our own with tetradentate ligands with tertiary phosphine and secondary amine donor groups were applied to improve the performance of these first iron(II) catalysts. In particular the correct positioning of a bifunctional H-Fe-NH unit in an iron hydride amine complex leads to exceptional catalyst activity because of the low energy barrier of dihydrogen transfer to the polar bond of the substrate. In addition the ligand structure with this NH group along with an asymmetric array of aryl groups orients the incoming substrate by hydrogen-bonding, and steric interactions provide the hydrogenated product in high enantioselectivity for several classes of substrates. Enantiomerically pure diamines or diphenylphosphino-amine compounds are used as the source of the asymmetry in the tetradentate ligands formed by the condensation of the amines with dialkyl- or diaryl-phosphinoaldehydes, a synthesis that is templated by Fe(II). The commercially available ortho-diphenylphosphinobenzaldehyde was used in the initial studies, but then diaryl-phosphinoacetaldehydes were found to produce much more effective ligands for iron(II). Once the mechanism of catalysis became clearer, the iron-templated synthesis of (S,S)-PAr2CH2CH2NHCHPhCHPhNH2 ligand precursors was developed to specifically introduce a secondary amine in the precatalyst structures. The reaction of a precatalyst with strong base yields a key iron-amido complex that reacts with isopropanol (in ATH) or dihydrogen (in AH) to generate an iron hydride with the Fe-H bond parallel to the secondary amine N-H. In the AH reactions, the correct acidity of the intermediate iron-dihydrogen complex and correct basicity of the amide are important factors for the heterolytic splitting of the dihydrogen to generate the H-Fe-N-H unit; the acidity of dihydrogen complexes including those found in hydrogenases can be estimated by a simple additive ligand acidity constant method. The placement of the hydridic-protonic Fe-H···HN interaction in the asymmetric catalyst structure influences the enantioinduction. The sense of enantioinduction is predictable from the structure of the H-Fe-N-H-containing catalyst interacting with the ketone in the same way as related H-Ru-N-H-containing catalysts. The modular construction of the catalysts permits large variations in order to produce alcohol or amine products with enantiomeric excess in the 90-100% range in several cases.